c3 complete - plantsbrook scienceplantsbrookscience.org.uk/c3 complete.pdfcomplete the sentences....

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Q1. Vinegar can be added to food. Vinegar is an aqueous solution of ethanoic acid.

Ethanoic acid is a weak acid.

(a) Which ion is present in aqueous solutions of all acids?

........................................................................................................................ (1)

(b) What is the difference between the pH of a weak acid compared to the pH of a strong acid of the same concentration?

Give a reason for your answer.

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........................................................................................................................ (2)

(c) The diagram shows the apparatus used to find the concentration of ethanoic acid in vinegar.

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(i) Why should phenolphthalein indicator be used for this titration instead of methyl orange?

...............................................................................................................

............................................................................................................... (1)

(ii) 25.00 cm3 of vinegar was neutralised by 30.50 cm3 of a solution of sodium hydroxide with a concentration of 0.50 moles per cubic decimetre.

The equation for this reaction is:

CH3COOH(aq) + NaOH(aq) → CH3COONa(aq) + H2O(l)

Calculate the concentration of ethanoic acid in this vinegar.

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Concentration of ethanoic acid in this vinegar = .................... moles per cubic decimetre

(2)

(d) The concentration of ethanoic acid in a different bottle of vinegar was 0.80 moles per cubic decimetre.

Calculate the mass in grams of ethanoic acid (CH3COOH) in 250 cm3 of this vinegar. The relative formula mass (Mr) of ethanoic acid = 60.

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Mass of ethanoic acid = ...................................... g (2)

(Total 8 marks)

Q2.This question is about organic compounds.

(a) Wine contains ethanol (CH3CH2OH).

(i) Complete the displayed structure of ethanol.

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(1)

(ii) Wine left in a glass for several days turns sour. The sour taste is caused by ethanoic acid.

Complete the sentences.

The ethanoic acid is produced from a reaction between ethanol

and ................................................... .

This type of reaction is ................................................... . (2)

(b) Propyl ethanoate, a fragrance, can be produced by reacting ethanoic acid with an alcohol.

Propyl ethanoate is a member of a series of organic compounds. The members of the series all have the same functional group.

The displayed structure of propyl ethanoate is:

(i) Draw a ring around the functional group for this series on the displayed structure of propyl ethanoate.

(1)

(ii) Name the series of organic compounds with this functional group.

............................................................................................................... (1)

(iii) The alcohol used to make propyl ethanoate has the formula CH3CH2CH2OH

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Name this alcohol.

............................................................................................................... (1)

(Total 6 marks)

Q3. The structures shown are of the first three members of a homologous series of alcohols.

(a) (i) Draw a ring around the correct general formula for alcohols.

CnH2n+1OH C2nH2n+1OH CnH2n+2OH (1)

(ii) What is the formula of the functional group for alcohols?

............................................................................................................... (1)

(b) Ethanol is the alcohol used in alcoholic drinks.

(i) When ethanol dissolves in water the solution formed is not alkaline.

Tick ( ) the reason why the solution formed is not alkaline.

Reason Tick ( )

Ethanol can be used as a solvent.

Ethanol dissolves in water to form hydroxide ions.

Ethanol has only covalent bonds in its molecule.

(1)

(ii) Ethanol is used as a fuel because ethanol burns in oxygen.

Complete and balance the chemical equation for this reaction.

C2H5OH + ................O2 → 2 CO2 + ................ (2)

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(c) Ethanol can be oxidised to produce the compound shown.

(i) Draw a ring around the correct answer to complete the sentence.

When this compound dissolves in water, the solution formed is

acidic.

alkaline.

neutral.

(1)

(ii) Ethanol reacts with this compound to produce the organic compound shown.

C2H5OH + CH3COOH → CH3COOC2H5 + H2O

Complete the sentence.

The type of organic compound produced is ......................................... . (1)

(Total 7 marks)

Q4. The structures shown are of the first two members of a homologous series of organic compounds.

Methanol Ethanol

(a) (i) Complete the diagram for propanol, the next member of the homologous series.

C ― C ― C

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Propanol (1)

(ii) Which one of the statements about ethanol is correct?

Tick ( ) one box.

Statement Tick ( )

Ethanol dissolves in water to form a neutral solution.

Ethanol reacts with sodium to produce chlorine.

Ethanol does not burn in air.

(1)

(b) Ethanoic acid (CH3COOH) can be produced from ethanol (CH3CH2OH).

(i) What type of reaction happens when ethanoic acid is produced from ethanol?

............................................................................................................... (1)

(ii) State one use of ethanoic acid.

............................................................................................................... (1)

(Total 4 marks

Q5. Vinegar can be added to food.

Vinegar is a solution of ethanoic acid in water.

(a) Ethanoic acid is a weak acid.

Draw a ring around the correct answer to complete each sentence.

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carbonate ions.

(i) When dissolved in water, an acid forms a solution containing hydrogen ions.

hydroxide ions.

(1)

completely ionised.

(ii) Ethanoic acid is a weak acid because in water it is not ionised.

partially ionised.

(1)

(b) The diagram shows the apparatus used to investigate the amount of ethanoic acid in vinegar.

(i) Draw a ring around the name of the piece of apparatus labelled A on the diagram.

burette measuring cylinder pipette

(1)

(ii) Phenolphthalein is added to the vinegar in the conical flask so that the end point of the titration can be seen.

What type of substance is phenolphthalein?

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Draw a ring around the correct answer.

alkali catalyst indicator

(1)

(iii) How would you know that the end point of the titration has been reached?

...............................................................................................................

............................................................................................................... (1)

(c) The results of the titration are shown in the table.

Rough titration Accurate titrations

1 2 3

Final reading in cm3 22 21.30 22.50 24.40

Initial reading in cm3 0 1.00 2.00 4.00

Volume used in cm3 22 20.30 20.50 20.40

Calculate the best value of the mean volume from these titrations.

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Mean volume used = ...................................... cm3

(2)

(d) 25.0 cm3 of this vinegar contained 1.25 g of ethanoic acid.

Calculate the mass of ethanoic acid in 1 litre (1000 cm3) of this vinegar.

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Mass = ................................................................ g (2)

(Total 9 mark

Q6. White vinegar can be made by distillation of brown malt vinegar.

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(a) White vinegar contains only water (boiling point 100 °C) and ethanoic acid (boiling point 118 °C).

Suggest why the brown colour remains in the flask during the distillation.

........................................................................................................................

........................................................................................................................ (1)

(b) Ethanoic acid is a weak acid.


completely

Weak acids are not ionised in water.

partially

(1)

(ii) Hydrochloric acid and ethanoic acid were reacted with magnesium metal to produce hydrogen gas.

At the start:

• both acids were the same concentration

• both pieces of magnesium were the same size.

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Give two observations which show that ethanoic acid is a weaker acid than hydrochloric acid.

1 ......................................................................................................................

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2 ......................................................................................................................

............................................................................................................... (2)

(c) A student did a titration to find out if the white vinegar contains 5 g of ethanoic acid in 100 cm3.

(i) Choose the correct words from the box to complete the sentences. Use each word once or not at all.

burette conical flask pipette thermometer

To do this titration 25.0 cm3 of the white vinegar is measured

using a ..................................................... .

The 25.0 cm3 of white vinegar is then run into a ..................................................... .

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An indicator is added to the white vinegar.

Sodium hydroxide solution is added to the white vinegar

from a ..................................................... . (3)

(ii) How does the student know when to stop adding the sodium hydroxide solution?

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............................................................................................................... (2)

(d) The titration is repeated three more times. The results are shown in the table.

Titration 1 2 3 4

Volume of sodium hydroxide in cm3 23.5 20.1 19.9 20.0

(i) The student decided that the mean of these results was 20.0 cm3.

Explain why. Use the figures from the table in your explanation.

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............................................................................................................... (2)

(ii) From the results, the student calculated that the concentration of the ethanoic acid was 48 g per cubic decimetre.

Did the white vinegar contain 5 g of ethanoic acid in 100 cm3 ? Explain your answer.

...............................................................................................................

............................................................................................................... (1)

(Total 12 marks)

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Q1. Food provides chemicals and energy to keep your body working. In your body, energy is released by respiration when glucose, C6H12O6, reacts with oxygen.

C6H12O6 + 6 O2 → 6 CO2 + 6 H2O

(a) The energy level diagram for the reaction of glucose with oxygen is shown.

(i) Which energy change, A, B or C, represents the activation energy?

(1)

(ii) Which energy change, A, B or C, shows that the reaction is exothermic?

(1)

(b) A student did an investigation to find the amount of energy released when 1 g of glucose burns in air.

The student:

• recorded the room temperature

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• placed 1 g of glucose into the crucible

• set up the equipment as shown in the diagram

• lit the glucose

• recorded the highest temperature of the water.

(i) One of the main errors in this experiment is energy loss to the surroundings.

Suggest one way that the equipment could be changed to reduce this energy loss.

...............................................................................................................

............................................................................................................... (1)

(ii) The room temperature was 20 °C and the highest temperature recorded was 42 °C. Use these temperature readings to calculate how much energy is released when 1 g of glucose burns. The equation that you need to use is:

Energy released in joules = 100 × 4.2 × temperature change

Show clearly how you work out your answer.

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Burning 1 g of glucose releases .............................. joules (2)

(iii) The amount of energy released by 1 g of glucose should be 16 000 J.

Apart from energy loss to the surroundings, suggest two other reasons why the student’s value was less than expected.

1 .............................................................................................................

...............................................................................................................

2 .............................................................................................................

............................................................................................................... (2)

(c) Suggest one reason why food labels provide information about the energy released

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by the food.

........................................................................................................................

........................................................................................................................ (1)

(Total 8 marks)

Q2. Vinegar can be added to food. Vinegar is an aqueous solution of ethanoic acid.

Ethanoic acid is a weak acid.

(a) Which ion is present in aqueous solutions of all acids?

........................................................................................................................ (1)

(b) What is the difference between the pH of a weak acid compared to the pH of a strong acid of the same concentration?


........................................................................................................................

........................................................................................................................ (2)

(c) The diagram shows the apparatus used to find the concentration of ethanoic acid in vinegar.

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(i) Why should phenolphthalein indicator be used for this titration instead of methyl orange?

...............................................................................................................

............................................................................................................... (1)

(ii) 25.00 cm3 of vinegar was neutralised by 30.50 cm3 of a solution of sodium hydroxide with a concentration of 0.50 moles per cubic decimetre.

The equation for this reaction is:

CH3COOH(aq) + NaOH(aq) → CH3COONa(aq) + H2O(l)

Calculate the concentration of ethanoic acid in this vinegar.

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

Concentration of ethanoic acid in this vinegar = .................... moles per cubic decimetre

(2)

(d) The concentration of ethanoic acid in a different bottle of vinegar was 0.80 moles per cubic decimetre.

Calculate the mass in grams of ethanoic acid (CH3COOH) in 250 cm3 of this vinegar. The relative formula mass (Mr) of ethanoic acid = 60.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

Mass of ethanoic acid = ...................................... g (2)

(Total 8 marks)

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Q3. You will find the information on the Data Sheet helpful when answering this question.

This equation shows the reaction between ethene and oxygen.

C2H4 + 3O2 → 2CO2 + 2H2O

The structural formulae in the equation below show the bonds in each molecule involved.

Use the three stages shown at (a), (b) and (c) below to calculate the nett energy transfer when the formula mass (1 mole) of ethene reacts with oxygen.

(a) Write down the bonds broken and the bonds formed during the reaction. (Some have already been done for you.)

(2)

(b) Calculate the total energy changes involved in breaking and in forming all of these bonds. (Some have already been done for you.)

(4)

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(c) Describe, as fully as you can, what the figures in (b) tell you about the overall reaction.

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..................................................................................................................................... (2)

(Total 8 marks)

Q4. A Bunsen burner releases heat energy by burning methane in air.

(a) Methane (CH4) reacts with oxygen from the air to produce carbon dioxide and water.

(i) Use the equation and the bond energies to calculate a value for the energy change in this reaction.

Bond Bond energy in kJ per mole

C — H 414

O ═ O 498

C ═ O 803

O–H 464

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Plantsbrook School

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Energy change = ................................ kJ per mole (3)

(ii) This reaction releases heat energy.

Explain why, in terms of bond energies.

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............................................................................................................... (2)

(b) If the gas tap to the Bunsen burner is turned on, the methane does not start burning until it is lit with a match.

Why is heat from the match needed to start the methane burning?

........................................................................................................................

........................................................................................................................ (1)

(Total 6 marks)

Q5.Read the information about energy changes and then answer the questions.

A student did an experiment to find the energy change when hydrochloric acid reacts with sodium hydroxide.

The equation which represents the reaction is:

HCl + NaOH → NaCl + H2O

The student used the apparatus shown in the diagram.

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The student placed 50 cm3 of hydrochloric acid in a glass beaker and measured the initial temperature.

The student then quickly added 50 cm3 of sodium hydroxide solution and stirred the mixture with the thermometer. The highest temperature was recorded.

The student repeated the experiment, and calculated the temperature change each time.

Experime

nt 1 Experime

nt 2 Experime

nt 3 Experime

nt 4

Initial temperature in °C

19.0 22.0 19.2 19.0

Highest temperature in °C

26.2 29.0 26.0 23.5

Temperature change in °C

7.2 7.0 6.8 4.5

(a) The biggest error in this experiment is heat loss.

Suggest how the apparatus could be modified to reduce heat loss.

........................................................................................................................

........................................................................................................................ (1)

(b) Suggest why it is important to mix the chemicals thoroughly.

........................................................................................................................ (1)

(c) Which one of these experiments was probably done on a different day to the others?


........................................................................................................................ (1)

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(d) Suggest why experiment 4 should not be used to calculate the average temperature change.

........................................................................................................................

........................................................................................................................ (1)

(e) Calculate the average temperature change from the first three experiments.

........................................................................................................................

Answer = .................................................. °C (1)

(f) Use the following equation to calculate the energy change for this reaction.

Energy change in joules = 100 × 4.2 × average temperature change

........................................................................................................................

Answer = .................................................. J (1)

(g) Which one of these energy level diagrams represents the energy change for this reaction?


........................................................................................................................

........................................................................................................................ (1)

(Total 7 marks)

Q6. The reaction between aluminium and iron oxide is used to weld together railway lines.

2Al(s) + Fe2O3(s) → 2Fe(l) + Al2O3(s)

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A simple, qualitative energy level diagram for this reaction is shown.

Use the energy level diagram to:

(i) describe the idea of activation energy;

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..................................................................................................................................... (1)

(ii) explain why the reaction produces molten iron.

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..................................................................................................................................... (2)

(Total 3 marks)

Q7. The balanced equation for the combustion of ethane is shown using structural formulae.

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(a) Complete the table to show the number of bonds broken and made when two molecules of ethane react with seven molecules of oxygen.

Type of bond Number of bonds broken

Number of bonds made

C –– C

C –– H

O ═ O

C ═ O

H –– O

(2)

(b) The combustion of ethane is a strongly exothermic process. Draw a labelled energy level diagram showing the endothermic and exothermic parts of the overall reaction. Indicate the activation energy on the diagram.

(4)

(c) Explain, in terms of particles and the activation energy of a reaction, how a catalyst is able to increase the rate of reaction.

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.................................................................................................................................... (2)

(Total 8 marks)

Q8. (a) (i) Which acid should the student add to sodium hydroxide solution to make sodium sulphate?

............................................................. acid (1)

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(ii) Use the table on the Data Sheet to help you to write the formula of sodium sulphate.

Formula: ........................................................................................................... (1)

(b) The student noticed that the solution in the beaker got warm when the acid reacted with the alkali. The energy diagram below represents this reaction.

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(i) In terms of energy, what type of reaction is this?

.......................................................................................................................... (1)

(ii) Use the energy diagram to calculate a value for the amount of energy released during this reaction.

..........................................................................................................................

Energy released .................... kJ (1)

(iii) Explain, in terms of bond breaking and bond forming, why energy is released during this reaction.

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........................................................................................................................... (3)

(iv) The reaction takes place very quickly, without the help of a catalyst. What does this suggest about the activation energy for this reaction?

...........................................................................................................................

........................................................................................................................... (1)

(Total 8 marks)

Q9. When a known mass of a hydrocarbon was completely burned in oxygen, 17.6 g of carbon dioxide and 7.2 g of water were the only products.

Relative formula masses (Mr): CO2 = 44; H2O = 18.

Use this information to calculate the number of moles of carbon dioxide and of water produced in this reaction. Use your answers to calculate the empirical formula of this hydrocarbon.

You must show your working to gain full marks.

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The empirical formula of this hydrocarbon is ......................................................... (3)

(Total 3 marks)

Q10. Hydrogen could be the fuel used in all cars. One advantage is that when hydrogen reacts with oxygen only water is produced.

The chemical equation for this reaction is:

2 H2 + O2 2H2O

This equation can be written showing the structural formulae.

2 H ― H + O ═ O 2 H ― O ― H

(a) Use the bond energies in the table to calculate the energy change for this reaction.

Bond Bond energy in kJ

H – H 436

O = O 498

O – H 464

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Energy change = .............................................. kJ (3)

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(b) Suggest why the bond energy of O = O is higher than the bond energies of both H – H and O – H.

........................................................................................................................

........................................................................................................................ (1)

(c) In terms of bond energies, explain why hydrogen can be used as a fuel

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........................................................................................................................ (2)

(Total 6 marks

Q11. The reaction of methane with steam is used in industry to make hydrogen.

(a) One of the reactions in this process is represented by this equation.

CH4 (g) + H2O CO (g) + 3H2 (g)

The forward reaction is endothermic.

State the conditions of temperature and pressure that would give the maximum yield of hydrogen.

Explain your answers.

(i) Temperature

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.......................................................................................................................... (2)

(ii) Pressure

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.......................................................................................................................... (2)

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(iii) Which one of the following metals is most likely to be a catalyst for this process? Draw a ring around your answer.

aluminium lead magnesium nickel sodium

Give a reason for your choice.

..........................................................................................................................

.......................................................................................................................... (1)

(b) A second stage in this process is represented by this equation.

(i) Use the bond energies given in the table to help you to calculate the nett energy transfer (energy change) for this reaction.

Bond Bond energy in kJ/mol

C ≡ O 1077

C = O 805

H – H 436

O – H 464

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Nett energy transfer = ...................................... kJ/mol (3)

(ii) State whether this reaction is exothermic or endothermic. .............................

Explain, by reference to your calculation, how you know.

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.......................................................................................................................... (2)

(Total 10 marks

Q1. The Haber process is used to make ammonia NH3. The table shows the percentage yield of ammonia at different temperatures and pressures.

PRESSURE (ATMOSPHERES)

PERCENTAGE (%) YIELD OF AMMONIA AT 350°C

PERCENTAGE (%) YIELD OF AMMONIA AT 500°C

50 25 5

100 37 9

200 52 15

300 63 20

400 70 23

500 74 25

(a) (i) Use the data in the table to draw two graphs on the grid below. Draw one graph for a temperature of 350°C and the second graph for a temperature of 500°C. Label each graph with its temperature.

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(4)

(ii) Use your graphs to find the conditions needed to give a yield of 30% ammonia.

................................ °C and .............................. atmospheres (1)

(iii) On the grid sketch the graph you would expect for a temperature of 450°C. (1)

(b) (i) This equation represents the reaction in which ammonia is formed.

N2(g) + 3H2(g) 2NH3(g) + heat

What does the symbol in this equation tell you about the reaction?

........................................................................................................................... (1)

(ii) Use your graphs and your knowledge of the Haber process to explain why a temperature of 450°C and a pressure of 200 atmospheres are used in industry.

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........................................................................................................................... (5)

(c) (i) Ammonium nitrate is one type of artificial fertiliser. Calculate the relative formula mass of ammonium nitrate NH4NO3. (Relative atomic masses: H = 1, N = 14, O = 16.)

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........................................................................................................................... (1)

(ii) Use your answer to part (c)(i) to help you calculate the percentage by mass of nitrogen present in ammonium nitrate NH4NO3.

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........................................................................................................................... (2)

(Total 15 marks)

Q2. Methanol is a fuel that is used in some racing cars instead of petrol.

Methanol can be made from carbon monoxide and hydrogen. The equation for this reaction is shown below.

CO(g) + 2H2(g) CH3OH(g)

The forward reaction is exothermic.

(a) A high pressure (between 50 and 100 atmospheres) is used in this process.

Explain why the highest equilibrium yield of methanol is obtained at high pressure.

.....................................................................................................................................

..................................................................................................................................... (1)

(b) The temperature used in this process is about 250 °C.

It has been stated that, ‘the use of this temperature is a compromise between the equilibrium yield of product and the rate of reaction’.

Explain this statement.

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..................................................................................................................................... (3)

(Total 4 marks)

Q3. Ammonia is made using the Haber process.

(a) How is ammonia separated from unreacted nitrogen and hydrogen in the separator?

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........................................................................................................................ (2)

(b) The equation shows the reaction which takes place in the reactor:

N2(g) + 3H2(g) 2NH3(g)

(i) Why does the yield of ammonia at equilibrium increase as the temperature is

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decreased?

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............................................................................................................... (1)

(ii) A temperature of 450 °C is used in the reactor to make the reaction take place quickly.

Explain, in terms of particles, why increasing the temperature makes a reaction go faster.

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(iii) Why does the yield of ammonia at equilibrium increase as the pressure is increased?

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............................................................................................................... (1)

(iv) The pressure used in the reactor is 200 atmospheres. Suggest why a much higher pressure is not used.

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............................................................................................................... (1)

(c) Use the equation for the reaction in the reactor to help you to answer these questions.

N2(g) + 3H2(g) 2NH3(g)

(i) It is important to mix the correct amounts of hydrogen and nitrogen in the reactor.

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20 m3 of nitrogen is reacted with hydrogen.

What volume of hydrogen (measured at the same temperature and pressure as the nitrogen) is needed to have the correct number of molecules to react with the nitrogen?

Volume of hydrogen needed = .......................... m3

(1)

(ii) Calculate the maximum mass of ammonia that can be made from 2 g of nitrogen.

Relative atomic masses: H = 1; N = 14.

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Maximum mass of ammonia = ............................ g (3)

(d) The expected maximum mass of ammonia produced by the Haber process can be calculated.

(i) In one process, the maximum mass of ammonia should be 80 kg.

The actual mass of ammonia obtained was 12 kg.

Calculate the percentage yield of ammonia in this process.

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Percentage yield of ammonia = ......................... % (1)

(ii) Give two reasons why it does not matter that the percentage yield of ammonia is low. Use the flow diagram at the start of this question to help you.

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............................................................................................................... (2)

(Total 14 marks)

Q4. Humberstone was a town in the desert of Northern Chile in South America. It was built for the people who worked in the nearby sodium nitrate mines.

The sodium nitrate was used as a fertiliser.

The sodium nitrate was exported by ship to countries all around the world.

Today the mines have closed and nobody lives in Humberstone.

One of the reasons for the mines closing was the invention of the Haber process.

By Sznegra (Own work) [CC-BY-SA-3.0], via Wikimedia Commons

(a) The Haber process is used to make ammonia (NH3).

N2(g) + 3H2(g) 2NH3(g)

The forward reaction is exothermic.

(i) Name the raw materials that are used to supply the nitrogen and hydrogen.

Nitrogen ............................................................

Hydrogen .......................................................... (2)

(ii) The Haber process uses a temperature of 450 °C.

Explain, as fully as you can, why a temperature of 450 °C is used rather than a much higher temperature or a much lower temperature.

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...............................................................................................................

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...............................................................................................................

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...............................................................................................................

...............................................................................................................

............................................................................................................... (3)

(iii) Ammonia can be converted to ammonium nitrate by adding an acid.

Name this acid.

............................................................................................................... (1)

(b) Suggest and explain why the invention of the Haber process caused the closure of the Humberstone mines in Chile.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................ (2)

(Total 8 marks)

Q5. Ammonia is manufactured from nitrogen and hydrogen in the Haber Process. The diagram shows some details of the manufacturing process.

(a) Nitrogen is obtained from the air.

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From where is the hydrogen obtained?

..................................................................................................................................... (1)

(b) What happens to the unreacted nitrogen and hydrogen?

.....................................................................................................................................

..................................................................................................................................... (1)

(c) Ammonium nitrate is made from ammonia. Farmers spread nitrates on to soil to make crops grow better. The nitrates may get into people’s bodies even if they do not eat the crops.

Explain how this can happen.

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(Total 4 mark

Q6. The equation for a reaction to produce hydrogen is:

CO(g) + H2O(g) CO2(g) + H2(g)

(a) Explain why changing the pressure does not affect the yield of hydrogen at equilibrium.

........................................................................................................................

........................................................................................................................ (1)

(b) Suggest why the best yield of hydrogen at equilibrium is obtained at low temperatures.

........................................................................................................................

........................................................................................................................ (1)

(c) The temperature used in industry needs to be high enough for the reaction to take place quickly. Explain, in terms of particles, why the rate of reaction increases when the temperature is increased.

........................................................................................................................

........................................................................................................................

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........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................ (3)

(d) Scientists have developed catalysts which allow the reaction to take place quickly at lower temperatures. How could this be good for the manufacturer and for the environment?

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................ (2)

(Total 7 marks)

Q7. The flow chart below shows the main stages in the production of ammonium nitrate.

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(i) Name the two raw materials shown in the flow chart as A and B by choosing words from the list.

air coke limestone natural gas

Raw material A ........................................................

Raw material B ........................................................ (2)

(ii) Complete the word equation for the reaction which makes ammonia.

....................................... + ....................................... → ammonia (1)

(iii) What is the purpose of the iron in the reactor?

.....................................................................................................................................

..................................................................................................................................... (1)

(iv) What is the purpose of pipe C?

.....................................................................................................................................

..................................................................................................................................... (1)

(Total 5 marks

Q8. Ammonia is made from nitrogen and hydrogen in the Haber process.

N2(g) + 3H2 (g) 2NH3 (g) (+ heat)

Flow Chart for the Haber Process

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Effect of temperature and pressure on the amount of ammonia at equilibrium

(a) Use the information given above and your knowledge of the Haber process and reversible reactions to help you to answer this question.

State which conditions of temperature and pressure would give the highest percentage of ammonia at equilibrium. Explain why.

.....................................................................................................................................

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.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (4)

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(b) The Haber process uses a temperature of 450 °C and a pressure of 200 atmospheres.

Explain why these conditions are chosen.

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.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (3)

(Total 7 marks)

Q9. Ammonium nitrate is an important chemical. The diagram shows the main stages in the manufacture of ammonium nitrate.

Study the diagram and then answer the question.

(a) What is the purpose of the iron in reactor 1?

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.....................................................................................................................................

..................................................................................................................................... (1)

(b) Explain why the best yield of ammonia at equilibrium is obtained:

(i) at low temperature

...........................................................................................................................

........................................................................................................................... (1)

(ii) at high pressure.

...........................................................................................................................

........................................................................................................................... (1)

(c) The temperature used in reactor 1 is 450 °C.

Explain why a much lower temperature is not used.

.....................................................................................................................................

..................................................................................................................................... (1)

(d) A mixture of ammonia, nitrogen and hydrogen leaves reactor 1.

In the separator, what is done to the mixture to separate the ammonia from the other gases?

.....................................................................................................................................

..................................................................................................................................... (1)

(Total 5 marks

Q1.Four bottles of chemicals made in the 1880s were found recently in a cupboard during a Health and Safety inspection at Lovell Laboratories.

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Sodium carbonate Sodium chloride

Sodium nitrate

Sodium sulfate

The chemical names are shown below each bottle.

(a) You are provided with the following reagents:

• aluminium powder

• barium chloride solution acidified with dilute hydrochloric acid

• dilute hydrochloric acid

• silver nitrate solution acidified with dilute nitric acid

• sodium hydroxide solution.

• limewater

• red litmus paper

(i) Describe tests that you could use to show that these chemicals are correctly named.

In each case give the reagent(s) you would use and state the result.

Test and result for carbonate ions:

...............................................................................................................

...............................................................................................................

...............................................................................................................

Test and result for chloride ions:

...............................................................................................................

...............................................................................................................

...............................................................................................................

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Test and result for nitrate ions:

...............................................................................................................

...............................................................................................................

...............................................................................................................

Test and result for sulfate ions:

...............................................................................................................

...............................................................................................................

............................................................................................................... (4)

(ii) Suggest why a flame test would not distinguish between these four chemicals.

............................................................................................................... (1)

(b) Instrumental methods of analysis linked to computers can be used to identify chemicals.

Give two advantages of using instrumental methods of analysis.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................ (2)

(Total 7 marks)

Q2. White vinegar can be made by distillation of brown malt vinegar.

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(a) White vinegar contains only water (boiling point 100 °C) and ethanoic acid (boiling point 118 °C).

Suggest why the brown colour remains in the flask during the distillation.

........................................................................................................................

........................................................................................................................ (1)

(b) Ethanoic acid is a weak acid.


completely

Weak acids are not ionised in water.

partially

(1)

(ii) Hydrochloric acid and ethanoic acid were reacted with magnesium metal to produce hydrogen gas.

At the start:

• both acids were the same concentration

• both pieces of magnesium were the same size.

Give two observations which show that ethanoic acid is a weaker acid than hydrochloric acid.

1 ......................................................................................................................

...............................................................................................................

2 ......................................................................................................................

...............................................................................................................

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(2)

(c) A student did a titration to find out if the white vinegar contains 5 g of ethanoic acid in 100 cm3.

(i) Choose the correct words from the box to complete the sentences. Use each word once or not at all.

burette conical flask pipette thermometer

To do this titration 25.0 cm3 of the white vinegar is measured

using a ..................................................... .

The 25.0 cm3 of white vinegar is then run into a ..................................................... .

An indicator is added to the white vinegar.

Sodium hydroxide solution is added to the white vinegar

from a ..................................................... . (3)

(ii) How does the student know when to stop adding the sodium hydroxide solution?

...............................................................................................................

...............................................................................................................

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...............................................................................................................

............................................................................................................... (2)

(d) The titration is repeated three more times. The results are shown in the table.

Titration 1 2 3 4

Volume of sodium hydroxide in cm3 23.5 20.1 19.9 20.0

(i) The student decided that the mean of these results was 20.0 cm3.

Explain why. Use the figures from the table in your explanation.

...............................................................................................................

...............................................................................................................

...............................................................................................................

............................................................................................................... (2)

(ii) From the results, the student calculated that the concentration of the ethanoic acid was 48 g per cubic decimetre.

Did the white vinegar contain 5 g of ethanoic acid in 100 cm3 ? Explain your answer.

...............................................................................................................

............................................................................................................... (1)

(Total 12 marks)

Q3. Cheshunt mixture is a powder containing copper sulfate, CuSO4, and ammonium carbonate, (NH4)2CO3

(a) A student tested the Cheshunt mixture.

(i) Hydrochloric acid was added. A gas was produced that turned limewater milky.


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The gas was .................................................................... which shows

that .................................................. ions are in the mixture. (2)

(ii) Sodium hydroxide solution was added. A gas was produced that indicates that ammonium ions are in the mixture.


The gas was .................................................................... which turns

damp red ...................................................................................... blue. (2)

(b) Cheshunt mixture is dissolved in water before it is used. When the student dissolved the Cheshunt mixture in water it formed a blue solution.

(i) Suggest how the student knew that copper ions are in this solution.

...............................................................................................................

............................................................................................................... (1)

(ii) The student tested the Cheshunt solution and the result of the test indicated that sulfate ions are in the solution.


The student added a solution of ............................... in the presence of

dilute hydrochloric acid and a ............................... precipitate was produced. (2)

(Total 7 marks)

Q4. Read the information in the box and then answer the questions.

Seidlitz Powder is the name of a medicine.

Seidlitz Powder comes as two powders. One powder is wrapped in white paper and contains tartaric acid (C4H6O6). The other powder is wrapped in blue paper and contains potassium sodium tartrate (KNaC4H4O6) and sodium hydrogencarbonate (NaHCO3).

The contents of the blue paper are completely dissolved in water and then the contents of the white paper are added.

The equation which represents this reaction is:

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C4H6O6 (aq) + 2NaHCO3 (aq) Na2C4H4O6 (aq) + 2H2O (l) + 2CO2 (g)

(a) Describe and give the result of a test to identify the gas produced in this reaction.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................ (2)

(b) One of the chemicals in Seidlitz Powder is potassium sodium tartrate (KNaC4H4O6).

Suggest why it would be difficult to identify both potassium ions and sodium ions in potassium sodium tartrate using a flame test.

........................................................................................................................

........................................................................................................................ (1)

(c) Some Seidlitz Powder was bought on the Internet. However, when tested, it was found to be only magnesium sulfate.

(i) Describe and give the result of a chemical test to show that magnesium sulfate contains sulfate ions.

Test .......................................................................................................

...............................................................................................................

Result ....................................................................................................

............................................................................................................... (2)

(ii) Magnesium sulfate contains magnesium ions.

Describe what you see when sodium hydroxide solution is added to a solution of magnesium sulfate.

...............................................................................................................

............................................................................................................... (1)

(Total 6 marks)

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Q5. Ammonia is made using the Haber process.

(a) How is ammonia separated from unreacted nitrogen and hydrogen in the separator?

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................ (2)

(b) The equation shows the reaction which takes place in the reactor:

N2(g) + 3H2(g) 2NH3(g)

(i) Why does the yield of ammonia at equilibrium increase as the temperature is decreased?

...............................................................................................................

............................................................................................................... (1)

(ii) A temperature of 450 °C is used in the reactor to make the reaction take place quickly.

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Explain, in terms of particles, why increasing the temperature makes a reaction go faster.

...............................................................................................................

...............................................................................................................

...............................................................................................................

............................................................................................................... (2)

(iii) Why does the yield of ammonia at equilibrium increase as the pressure is increased?

...............................................................................................................

............................................................................................................... (1)

(iv) The pressure used in the reactor is 200 atmospheres. Suggest why a much higher pressure is not used.

...............................................................................................................

............................................................................................................... (1)

(c) Use the equation for the reaction in the reactor to help you to answer these questions.

N2(g) + 3H2(g) 2NH3(g)

(i) It is important to mix the correct amounts of hydrogen and nitrogen in the reactor.

20 m3 of nitrogen is reacted with hydrogen.

What volume of hydrogen (measured at the same temperature and pressure as the nitrogen) is needed to have the correct number of molecules to react with the nitrogen?

Volume of hydrogen needed = .......................... m3

(1)

(ii) Calculate the maximum mass of ammonia that can be made from 2 g of

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nitrogen.

Relative atomic masses: H = 1; N = 14.

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

Maximum mass of ammonia = ............................ g (3)

(d) The expected maximum mass of ammonia produced by the Haber process can be calculated.

(i) In one process, the maximum mass of ammonia should be 80 kg.

The actual mass of ammonia obtained was 12 kg.

Calculate the percentage yield of ammonia in this process.

...............................................................................................................

...............................................................................................................

Percentage yield of ammonia = ......................... % (1)

(ii) Give two reasons why it does not matter that the percentage yield of ammonia is low. Use the flow diagram at the start of this question to help you.

...............................................................................................................

...............................................................................................................

...............................................................................................................

............................................................................................................... (2)

(Total 14 marks)

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Q6. Powdered magnesium oxide was added in 0.1 g amounts to 25 cm3 of dilute hydrochloric acid and the mixture stirred. The powder soon reacted and disappeared, but after about 1.0 g had been added it took some time for all the solid to react. When a total of 1.1 g of powder had been added, some of the magnesium oxide remained at the bottom of the flask.

(a) On the following axes draw a sketch graph to show how the pH of the liquid is likely to change during the experiment described above. Start the graph with the pH of the acid before any magnesium oxide is added.

(3)

(b) A second experiment was done using magnesium oxide from the same bottle with 25 cm3 of the same hydrochloric acid.

There is no catalyst for this reaction. Suggest two ways in which the rate of this reaction could have been speeded up.

...................................................................................................................................

................................................................................................................................... (2)

(c) (i) What is the symbol for the oxide ion?

...........................................................................................................................

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(1)

(ii) Complete the ionic equation for the reaction between hydrogen ions and oxide ions.

................................. + ................................. → H2O (2)

(iii) The experiment was repeated, but 25 cm3 of dilute sulphuric acid was used instead of hydrochloric acid.

The concentration of the sulphuric acid was the same as the hydrochloric acid (0.1 M).

Why was twice as much magnesium oxide needed to neutralise the sulphuric acid completely?

...........................................................................................................................

........................................................................................................................... (1)

(Total 9 marks

Q7.In this question you will be assessed on using good English, organising information clearly and using specialist terms where appropriate.

A student used the equipment shown to do a titration.

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Describe how the student should use this equipment to find the volume of sodium hydroxide solution that reacts with a known volume of acid. Include any measurements the student should make.

Do not describe how to do any calculations.

.................................................................................................................................

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.................................................................................................................................

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................................................................................................................................. (Total 6 marks)

Q8. The label is from a packet of Low Sodium Salt.

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(a) A student tested some Low Sodium Salt to show that it contains carbonate ions and chloride ions.

(i) Describe and give the result of a test for carbonate ions.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(ii) A student identified chloride ions using acidified silver nitrate solution.

State what you would see when acidified silver nitrate solution is added to a solution of Low Sodium Salt.

........................................................................................................................... (1)

(iii) Flame tests can be used to identify potassium ions and sodium ions.

Suggest why it is difficult to identify both of these ions in Low Sodium Salt using a flame test.

...........................................................................................................................

........................................................................................................................... (1)

(b) Read the following information and then answer the questions.

Salt – friend or foe?

Sodium chloride (salt) is an essential mineral for our health. It is used to flavour and preserve foods. Too much sodium in our diet may increase the risk of high blood pressure and heart disease. Heart disease is the biggest cause of death in the United Kingdom. Some people claim that excess sodium is a poison that can cause cancer, while others say that more evidence is needed.

Many processed foods contain salt, so it is easy to exceed the recommended daily upper limit of about 5 g of salt per person. A ‘healthier’ amount should be about 3 g. In the United Kingdom many people consume over 10 g of salt each day.

One way to reduce sodium in our diet is to use Low Sodium Salt. This has two thirds of the sodium chloride replaced by potassium chloride.

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A national newspaper asked readers for their views on two options.

Option 1: Ban the use of sodium chloride in foods.

Option 2: Reduce the amount of sodium chloride in all foods to a ‘healthier’ level.

(i) Suggest why Option 1 was rejected.

...........................................................................................................................

........................................................................................................................... (1)

(ii) Suggest two advantages and one disadvantage of Option 2.

...........................................................................................................................

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........................................................................................................................... (3)

(Total 8 mark

Q9. (a) This label has been taken from a bottle of vinegar.

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Vinegar is used for seasoning foods. It is a solution of ethanoic acid in water.

In an experiment, it was found that the ethanoic acid present in a 15.000 cm3 sample of vinegar was neutralised by 45.000 cm3 of sodium hydroxide solution, of concentration 0.20 moles per cubic decimetre (moles per litre).

The equation which represents this reaction is

CH3COOH + NaOH → CH3COONa + H2O

Calculate the concentration of the ethanoic acid in this vinegar:

(i) in moles per cubic decimetre (moles per litre);

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

Concentration =................................... moles per cubic decimetre (2)

(ii) in grams per cubic decimetre (grams per litre).

Relative atomic masses: H = 1; C = 12; O = 16.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

Concentration = .................................. grams per cubic decimetre (2)

(b) The flow diagram shows some reactions of ethanoic acid.

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Give the name of:

(i) gas A,

............................................................................................................................ (1)

(ii) alkali B,

............................................................................................................................ (1)

(iii) ester C,

............................................................................................................................ (1)

(iv) catalyst D,

............................................................................................................................ (1)

(v) carboxylic acid salt E.

............................................................................................................................ (1)

(Total 9 marks)

Q10. Ammonium sulfate is an artificial fertiliser.

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(a) (i) When this fertiliser is warmed with sodium hydroxide solution, ammonia gas is given off. Describe and give the result of a test for ammonia gas.

Test .......................................................................................................

...............................................................................................................

Result ...................................................................................................

............................................................................................................... (2)

(ii) Describe and give the result of a chemical test to show that this fertiliser contains sulfate ions (SO4

2–).

Test .......................................................................................................

...............................................................................................................

Result ...................................................................................................

............................................................................................................... (2)

(b) Ammonium sulfate is made by reacting sulfuric acid (a strong acid) with ammonia solution (a weak alkali).

(i) Explain the meaning of strong in terms of ionisation.

............................................................................................................... (1)

(ii) A student made some ammonium sulfate in a school laboratory

The student carried out a titration, using a suitable indicator, to find the volumes of sulfuric acid and ammonia solution that should be reacted together.

Name a suitable indicator for strong acid-weak alkali titrations.

............................................................................................................... (1)

(iii) The student found that 25.0 cm3 of ammonia solution reacted completely with 32.0 cm3 of sulfuric acid of concentration 0.050 moles per cubic decimetre.

The equation that represents this reaction is:

2H2SO4(aq) + 2NH3(aq) → (NH4)2SO4 (aq)

Calculate the concentration of this ammonia solution in moles per cubic decimetre.

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...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

Concentration = .................................. moles per cubic decimetre (3)

(iv) Use your answer to (b)(iii) to calculate the concentration of ammonia in grams per cubic decimetre.

(If you did not answer part (b)(iii), assume that the concentration of the ammonia solution is 0.15 moles per cubic decimetre. This is not the correct answer to part (b)(iii).)

Relative formula mass of ammonia (NH3) = 17.

...............................................................................................................

...............................................................................................................

...............................................................................................................

Concentration = .................................. grams per cubic decimetre (2)

(Total 11 marks)

Q11. This label has been taken from a packet of My Baby Food.

MY BABY FOOD

Infant milk

Pure and natural

Closest to mothers’ breast milk

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Contains traces of essential minerals

500 g

One of the minerals in My Baby Food is calcium carbonate, CaCO3.

(a) Chemical tests are used to identify elements and compounds.

(i) A flame test can be used to identify calcium ions. What colour do calcium ions give in a flame test?

........................................................................................................................... (1)

(ii) When a flame test was carried out on My Baby Food, the presence of calcium ions was not seen. A yellow flame was produced. Name the ion which gives a yellow flame test.

........................................................................................................................... (1)

(iii) Suggest one advantage of using an instrumental method to detect the elements present in My Baby Food.

...........................................................................................................................

........................................................................................................................... (1)

(iv) Name an instrumental method for detecting elements.

........................................................................................................................... (1)

(b) Read the information in the box below and then answer the question.

Calcium carbonate occurs naturally as marble and limestone. They are important building materials and are often used for gravestones.

Calcium carbonate is also an essential mineral for good health and is present in many baby foods in small amounts.

My Baby Food is recommended as being the closest to a mother’s own breast milk. It is given free to mothers in the developing world – without it their babies might die of malnutrition.

Responsible Mothers Are Us (RMAU) is a United Kingdom pressure group. They want to ban chemicals in baby foods. The group was founded by Mrs I. M. Right who has made a career in ‘goodness’ and is paid from donations given to RMAU by members of the public.

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When interviewed, she said: “Calcium carbonate is a chemical and so it is a pollutant. My Baby Food must be banned to prevent the mass medication of babies. I don’t feed my baby the stuff of gravestones.”

Many people do not agree with Mrs Right’s ideas.

Suggest why.

.....................................................................................................................................

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.....................................................................................................................................

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.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (3)

(Total 7 marks)

Q12. (a) Four bottles of chemicals made in the 1880s were found recently in a cupboard during a Health and Safety inspection at Lovell Laboratories.

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The chemicals are correctly named.

You are provided with the following reagents:

• aluminium powder

• barium chloride solution acidified with dilute hydrochloric acid

• dilute hydrochloric acid

• silver nitrate solution acidified with dilute nitric acid

• sodium hydroxide solution.

(i) Describe tests to show that these chemicals are correctly named.

In each case give the reagent(s) you would use and state what you would see.

Test and result for carbonate ions:

...........................................................................................................................

...........................................................................................................................

Test and result for chloride ions:

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...........................................................................................................................

...........................................................................................................................

Test and result for nitrate ions:

...........................................................................................................................

...........................................................................................................................

Test and result for sulfate ions:

...........................................................................................................................

........................................................................................................................... (5)

(ii) Suggest why a flame test would not distinguish between these four chemicals.

........................................................................................................................... (1)

(b) Instrumental methods of analysis linked to computers can be used to identify chemicals.

Describe two advantages of using instrumental methods of analysis.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(Total 8 marks

Q1. John Newlands was a chemist who worked in a sugar factory.

In 1866 he designed a periodic table. He arranged the elements in order of their relative atomic masses.

He found a repeating pattern for some of the elements. Newlands wrote, ‘the eighth element starting from a given one, is a kind of repetition of the first, like the eighth note in an octave of music’.

H Li G Bo C N O

F Na Mg Al Si P S

Cl K Ca Cr Ti Mn Fe

Co, Ni Cu Zn Y In As Se

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Br Rb Sr Ce, La Zr Di, Mo Ro, Ru

Pd Ag Cd U Sn Sb Te

I Cs Ba, V Ta W Nb Au

Pt, Ir Tl Pb Th Hg Bi Os

Newlands’ periodic table

(a) In Newlands’ periodic table, the elements lithium, sodium and potassium are grouped together.

Give two properties of these elements which support the idea that they should be grouped together.

1 ......................................................................................................................

........................................................................................................................

2 ......................................................................................................................

........................................................................................................................ (2)

(b) Newlands’ periodic table was not accepted by most chemists in 1866.

Suggest reasons why. Use the Newlands’ periodic table above to help you to answer this question.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

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........................................................................................................................ (3)

(c) State and explain one way in which Mendeleev improved Newlands’ periodic table.

........................................................................................................................

........................................................................................................................

........................................................................................................................

Plantsbrook School

........................................................................................................................ (2)

(Total 7 marks)

Q2. The halogens are in Group 7 of the periodic table.

(a) Why, in terms of electrons, are the halogens in Group 7?

........................................................................................................................

........................................................................................................................ (1)

(b) Sea water contains bromide ions (Br-). The bromide ions can be changed to bromine by bubbling chlorine gas into sea water. Chlorine is able to displace bromine from sea water because chlorine is more reactive than bromine.

2Br-(aq) + Cl2(g) → Br2(g) + 2Cl-(aq)

Explain, in terms of electrons, why chlorine is more reactive than bromine.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................ (3)

(Total 4 marks)

Q3. Read the information about protecting the bottoms of ships.

A Copper-bottomed Investment

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From the 16th to the 19th century, the bottoms of many wooden ships were protected from marine organisms by being covered with sheets of metal.

At first lead was used on the bottoms of ships, then copper was used until 1832 when Muntz Metal replaced it. Muntz Metal is an alloy of two transition metals, copper and zinc.

Table of data

Lead Copper Muntz Metal

Cost (£/kg) £1.20 £3.20 £2.30

Melting point (°C) 327 1083 904

Stops sea worms attacking wood Yes Yes Yes

Stops barnacles and seaweed sticking to the bottom of the ship

No Yes Yes

(a) Use the information to answer the following questions.

(i) Suggest why copper replaced lead.

...............................................................................................................

............................................................................................................... (1)

(ii) Suggest why Muntz Metal replaced copper.

...............................................................................................................

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............................................................................................................... (1)

(b) A sample of Muntz Metal contains a very small amount of iron as an impurity.

(i) Name an instrumental method of analysis that could be used to detect iron.

............................................................................................................... (1)

(ii) Suggest why an instrumental method would detect the iron in this sample of Muntz Metal but a chemical method is not likely to be successful.

...............................................................................................................

............................................................................................................... (1)

(c) Today, ships are made from steel. Steels are alloys of iron, a transition metal.

Give two properties of transition metals that make them suitable for making ships.

Property 1 ......................................................................................................

........................................................................................................................

Property 2 ......................................................................................................

........................................................................................................................ (2)

(Total 6 marks)

Q4. (a) The table gives the melting points of some of the elements of Group 7.

Element Atomic number Melting point in ºC

Fluorine 9 –220

Chlorine 17 –101

Bromine 35 –7

Iodine 53 114

Astatine 85 ?

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(i) Plot a graph of the melting point against atomic number.

Draw a line of best fit. Extend your line to estimate a value for the melting point of astatine.

(2)

(ii) Estimate the melting point of astatine. ........................................................ °C (1)

(iii) Which of the Group 7 elements are solids at 20 °C?

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(b) (i) Draw a diagram to show the arrangement of electrons in an atom of fluorine.

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(1)

(ii) The elements of Group 7 have similar chemical properties.

Explain, in terms of electrons, why they have similar chemical properties.

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(c) Xenon is a very unreactive element.

(i) Explain, in terms of electrons, why xenon is so unreactive.

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(ii) Fluorine reacts with xenon but iodine does not.

Explain, in terms of atomic structure, why fluorine is more reactive than iodine.

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(Total 11 marks

Q5. (a) Dimitri Mendeleev was one of the first chemists to classify the elements by arranging them in order of their atomic weights. His periodic table was published in 1869.

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By unknown / неизвестен (here / здесь) [Public domain], via Wikimedia Commons

How did Mendeleev know that there must be undiscovered elements and how did he take this into account when he designed his periodic table?

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(b) By the early 20th century protons and electrons had been discovered.

Describe how this discovery allowed chemists to place elements in their correct order and correct group.

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(c) The transition elements are a block of elements between Groups 2 and 3 of the periodic table.

(i) Transition elements have similar properties.

Explain why in terms of electronic structure.

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(ii) There are no transition elements between the Group 2 element magnesium and the Group 3 element aluminium.

Explain why in terms of electronic structure.

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(Total 8 marks)

Q6. In 1999 scientists at the University of Berkeley claimed to have discovered the element Ununhexium.

The electron arrangement of this element is thought to be as shown in the diagram below.

(a) Which group of the periodic table should this element be placed in?

Group ............................. (1)

(b) Give a reason for your answer.

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(1) (Total 2 marks)

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Q7. (a) The table shows how Group 7 elements react with hydrogen.

Element Reaction with hydrogen

Description Product

Fluorine Explosive reaction in dim light Hydrogen fluoride

Chlorine Explosive reaction in sunlight Hydrogen chloride

Bromine Reacts if heated Hydrogen bromide

Iodine Reacts if heated strongly Hydrogen iodine

(i) Explain why all the Group 7 elements react in a similar way with hydrogen.

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(ii) Explain the difference in the rates of the reaction of fluorine with hydrogen, and of iodine with hydrogen.

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(b) Explain why Group 0 elements are monatomic.

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(Total 6 marks)

Q8. The electronic structures of five elements, V, W, X, Y and Z are shown below.

(a) (i) Write the letters of the two elements which belong to the same group in the

Periodic Table ..................................................................................................

(ii) To which group do they belong? ..................................................................... (2)

(b) Write the letters of two elements that are gases ........................................................ (1)

(c) Lithium, sodium and potassium are the first three elements in Group 1 of the Periodic Table.

(i) Lithium reacts with cold water to produce lithium hydroxide and hydrogen.

Describe how the reaction between sodium and water is

(A) similar and (B) different to that between lithium and water.

(A) Similar ........................................................................................................

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(B) Different .....................................................................................................

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(ii) Potassium is much more reactive than lithium.

Explain this in terms of their electronic structures.

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(Total 9 marks)

Q9. The following article appeared recently in the Manchester Gazette.

Sodium Drum Blaze Scare

A 20 litre drum containing sodium burst into flames when it reacted violently with rainwater at a Manchester factory. It is believed that the sodium, which is normally stored under oil, had been accidentally left outside with the lid off.

A factory worker put out the blaze before the fire services arrived, and a leading fire fighter said, “It was fortunate that potassium wasn’t involved as it would have reacted more violently and exploded. These Group 1 alkali metals can be very dangerous”.

(a) Group 1 metals are stored under oil.

Suggest why.

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(b) Balance the equation which represents the reaction between sodium and water.

Na + H2O → NaOH + H2

(1)

(c) Explain why the Group 1 metals are called the alkali metals.

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(d) Explain, in terms of electrons, why potassium reacts more violently than sodium.

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(Total 6 mark

Q10.(a) Dmitri Mendeleev was one of the first chemists to classify the elements by arranging them in order of their atomic weights. His periodic table was published in 1869.

How did Mendeleev know that there must be undiscovered elements and how did he take this into account when he designed his periodic table?

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(b) By the early 20th century protons and electrons had been discovered.

Describe how knowledge of the numbers of protons and electrons in atoms allow chemists to place elements in their correct order and correct group.

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(c) The transition elements are a block of elements between Groups 2 and 3 of the periodic table.

(i) Transition elements have similar properties.

Explain why, in terms of electronic structure.

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(ii) There are no transition elements between the Group 2 element magnesium and the Group 3 element aluminium.

Give a reason why, in terms of electronic structure.

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(Total 8 marks

Q1. In some parts of the UK, the water is hard.

(a) As rain falls through the air, carbon dioxide dissolves in the water. The graph shows the solubility of carbon dioxide in water at different temperatures.

(i) Complete the graph by drawing a smooth curve through the points. (1)

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(ii) Use the graph to find the mass of carbon dioxide that dissolves in water at 50 °C.

Mass = ................................... g (1)

(iii) Calculate the mass of carbon dioxide that bubbles out of 100 g of water when the temperature rises from 20 °C to 60 °C.

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Mass = ................................... g (2)

(b) Hard water contains dissolved calcium compounds. Carbon dioxide dissolved in water reacts with calcium carbonate in limestone. The product is calcium hydrogencarbonate which dissolves in water.

CaCO3(s) + H2O(l) + CO2(g) Ca(HCO3)2(aq)

When this hard water is heated, an insoluble scale is produced. Use the chemical equation to explain how this happens.

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(c) This label was on a dishwasher.

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This dishwasher has a built-in water softener.

Use the information and your knowledge and understanding to explain how sodium chloride helps to soften the water in this dishwasher.

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(Total 10 marks)

Q2. In the United Kingdom, water companies supply drinking water to our homes. However, some people are concerned about the taste and quality of the water that is supplied.

Describe one method that people can use at home to improve the taste and quality of the tap water supplied. Explain how this method works.

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Plantsbrook School

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(Total 4 marks)

Q3. Read the following information and then answer the questions.

Chlorine – for better, for worse?

Chlorine is used to make bleaches, plastics and medicines. Swimming pool water is often treated with chlorine.

Chlorine is used to make water safe to drink. It is relatively cheap and easy to use. People who drink untreated water risk dying from typhoid and cholera.

However, chlorine is a poisonous chemical. It causes breathing difficulties and can kill people. Some people are also allergic to chlorine.

(a) How does chlorine make water safe to drink?

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(b) The amount of chlorine in swimming pool water should be carefully monitored and controlled.

Explain why.

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(c) Developing countries are likely to choose chlorination as their method of making water safe to drink.

Suggest why.

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(d) A government is setting up an enquiry into the safety of using chlorine.

(i) Suggest why people from all political parties should be represented.

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(ii) Suggest why the opinion of a well-respected scientist might change the outcome of any discussion.

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(iii) The decision taken about the safety of using chlorine should be based on evidence and data rather than on hearsay and opinion.

Suggest why.

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Plantsbrook School

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(Total 7 marks)

Q4. The table gives some information about the composition of three samples of water from wells in the Canary Islands, Crete and Cyprus.

Mineral content of water in mg per litre

Ions Canary Islands Crete Cyprus

Calcium, Ca2+ 28 82 18

Magnesium, Mg2+ 14 41 13

Sodium, Na+ 53 7 22

Chloride, Cl– 7 143 39

Hydrogencarbonate, HCO3– 281 5 93

Sulfate, SO42– 2 14 16

(a) Describe and explain how ions get into these samples of water.

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(b) The sample of water from Crete is harder than the other two.

Use the information in the table to explain why.

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(c) People who use hard water can expect higher costs than people who use soft water.

Explain why.

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(d) Hard water can be made soft by removing the ions that cause hardness.

State one way these ions can be removed.

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(Total 6 marks)

Q5. Two problems of hard water are scale and scum, as shown in the pictures of a heating element and a wash basin.

(a) Explain the difference between scale and scum

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(b) Explain how hard water can be made soft using an ion-exchange column.

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(Total 4 marks)

Q6. The label shows the ions present in the bottle of spring water. This water is temporarily hard.

(a) Name the compound that would be present in the greatest amount if this water were evaporated to dryness.

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(b) (i) What is hard water?

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(ii) State one advantage of hard water.

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(c) Describe an experiment that would show that this water is temporarily hard.

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(4)

(d) This hard water may be softened as shown.

What name is given to this process?

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(Total 10 marks)

Q7.(a) A campsite has a spring, where hard water flows out of limestone rock.

A student compared the hardness of the spring water with two other samples of water.

The student measured 20 cm3 of water into a boiling tube.

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The student then:

• added a drop of soap solution

• shook the boiling tube for 10 seconds

• looked to see if a permanent lather had formed.

The student repeated the procedure until a permanent lather formed.

The results are shown in the table.

Water sample

Number of drops of soap solution needed to form a permanent lather

Test 1 Test 2 Test 3 Mean

Spring water (from the campsite) 13 11 6

Tap water 7 5 6 6

Distilled water 1 1 1 1

(i) Calculate the correct mean for spring water.

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Mean = .......................... drops (2)

(ii) What conclusion could the student make from her results?

Use the results in the table to give a reason for your answer.

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(iii) Another student at the campsite boils some of the hard spring water in a pan. The inside of the pan becomes coated with a white solid.

Explain how the white solid is produced.

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(b) Ion exchange columns can be used to soften hard water.

(i) Describe how an ion exchange column softens water.

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(ii) An ion exchange column is used for a few weeks.

Sodium chloride solution now needs to be passed through the ion exchange

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column.

Suggest why.

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(c) Tap water in the UK is safe to drink because water companies add chlorine to sterilise the water.

Suggest one argument for and one argument against water companies adding chlorine to sterilise water.

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(Total 13 marks)

c3 complete - plantsbrook scienceplantsbrookscience.org.uk/c3 complete.pdfcomplete the sentences....

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