c2 foundation revision questions - sets 3,4&5

8/19/2019 C2 Foundation Revision Questions - Sets 3,4&5

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11 3,4,5 - Chemistry Mock Exam Revision - Foundation

C2.4 Rates of reaction Revision Foundation

Q1. Pieces of zinc react with dilute acid to form hydrogen gas.

The graph shows how the volume of hydrogen gas produced changes with time.

(a) Describe, as fully as you can, how the volume of gas produced changes with time.

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

.....................................................................................................................................(

(b) A student wants to make the reaction take place faster.

Some suggestions are given in the table.

Put ticks ( ) next to the two suggestions that would make the reaction take place faster.

Suggestions ( )

Use bigger pieces of zinc.

Use a more concentrated acid.

Use zinc powder.

Decrease the temperature of the acid.

((Total 4 mark


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Q2. Hydrogen peroxide (H2O2) contains the same elements as water (H2O).

(a) Name the hazard symbol shown by using the correct word from the box.

corrosive flammable oxidising toxic

(

(b) Hydrogen peroxide decomposes in the presence of a catalyst.

2H2O2(aq) → 2H2O(l) + O2(g)

(i) Complete the word equation for this chemical reaction.

hydrogen peroxide → water + ................................(

(ii) What does a catalyst do to a chemical reaction?

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

...........................................................................................................................(

(Total 3 mark

Q3. A student investigated the rate of reaction between marble and hydrochloric acid.

The student used an excess of marble.

The reaction can be represented by this equation:

CaCO3(s) + 2HCl (aq) → CaCl 2(aq) + H2O(l ) + CO2(g)

The student used the apparatus shown in the diagram.


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The student measured the mass of the flask and contents for ten minutes.

The results are shown on the graph. Use the graph to answer the questions.

(a) (i) Complete the graph by drawing a line of best fit.(

(ii) Use the graph to find the mass of the flask and contents after 1.8 minutes.

................................. grams

(

(iii) The rate of reaction can be measured by the steepness of the graph line.

Describe, as fully as you can, how the rate of reaction changes with time in this experiment.

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

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

...............................................................................................................(


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(b) The mass of the flask and contents decreased during the experiment.

Use the equation for this reaction to help you explain why.

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

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

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

........................................................................................................................(

(c) A balance is used to measure the mass of the apparatus.

(i) Which balance, A, B, or C, has the highest resolution (most precise)?

Balance A Balance B Balance C

The balance with the highest resolution is balance(

(ii) The balance used for this experiment should have a high resolution.

Explain why.

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

...............................................................................................................(

(d) The student repeated the experiment using powdered marble instead of marble chips.

The rate of reaction between the marble and hydrochloric acid particles was much faster with thepowder.

Explain why.

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

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

........................................................................................................................(

(Total 11 mark


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Q4. A student studied the effect of temperature on the rate of reaction between hydrochloric acid andsodium thiosulphate.

• The student mixed 50 cm3 of a sodium thiosulphate solution and 5 cm3 of hydrochloric acid in aflask.

• The flask was placed over a cross.

• The student timed how long after mixing the cross could no longer be seen.

(a) (i) Balance the chemical equation for this reaction.

Na2S2O3(aq) + HCl(aq) → NaCl(aq) + H2O(l) + SO2(g) + S(s)(

(ii) What causes the cross to be seen no longer?

..........................................................................................................................(

(b) A graph of the results is shown.

(i) What effect does temperature have on the rate of this reaction?

..........................................................................................................................(


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(ii) Explain why temperature has this effect on the rate of reaction.

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

..........................................................................................................................(

(Total 5 mark

Q5. Sodium thiosulfate solution reacts with hydrochloric acid. As the reaction takes place the solutionslowly turns cloudy.

The diagram shows a method of measuring the rate of this reaction.

A student used this method to investigate how changing the concentration of the sodium thiosulfatesolution affects the rate of this reaction. The student used different concentrations of sodiumthiosulfate solution. All the other variables were kept the same. The results are shown on the graph

below.


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(a) (i) Draw a line of best fit on the graph.(

(ii) Suggest two reasons why all of the points do not lie on the line of best fit.

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

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

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

...........................................................................................................................(

(b) (i) In a conclusion to the investigation the student stated that:

‘The rate of this reaction is directly proportional to the concentration of the sodiumthiosulfate solution.’

How does the graph support this conclusion?

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

...........................................................................................................................(

(ii) Explain, in terms of particles, why the rate of reaction increases when the concentration ofsodium thiosulfate is increased.

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

...........................................................................................................................(

(Total 6 mark

Q6. A student investigated the rate of reaction between marble and hydrochloric acid.

The student used an excess of marble.

The reaction can be represented by this equation.

CaCO3 (s) + 2HC1 (aq) → CaC12 (aq) + H2O (l) + CO2 (g)

The student used the apparatus shown in the diagram.


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The student measured the mass of the flask and contents every half minute for ten minutes.

The results are shown on the graph. Use the graph to answer the questions.

(a) Complete the graph opposite by drawing a line of best fit.(

(b) Why did the mass of the flask and contents decrease with time?

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

.....................................................................................................................................(

(c) After how many minutes had all the acid been used up?

.............................. minutes(

(d) The student repeated the experiment at a higher temperature. All other variables were kept thesame as in the first experiment. The rate of reaction was much faster.

(i) Draw a line on the graph to show what the results for this second experiment might looklike.

(

(ii) Why does an increase in temperature increase the rate of reaction?

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

...........................................................................................................................(

(Total 8 mark


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(b) (i) When is the rate of reaction at its fastest?

..........................................................................................................................(

(ii) State one way in which she could increase the rate of reaction.

..........................................................................................................................(

(c) (i) What is the total volume of hydrogen collected in the experiment?

................................................................................................................... cm³(

(ii) State one way in which she could increase the final volume of hydrogen collected.

..........................................................................................................................(

Q8. Calcium carbonate reacts with dilute hydrochloric acid as shown in the equation below.

CaCO3(s) + 2HCl(aq) → CaCl2(aq) + H2O(l) + CO2(g)

The rate at which this reaction takes place can be studied by measuring the amount of carbon dioxidegas produced. The graph below shows the results of four experiments, 1 to 4. In each experiment theamount of calcium carbonate, the volume of acid and the concentration of the acid were kept the samebut the temperature of the acid was changed each time. The calcium carbonate was in the form ofsmall lumps of marble.

(a) Apart from altering the temperature, suggest two ways in which the reaction of calciumcarbonate and hydrochloric acid could be speeded up.

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

2. ................................................................................................................................(


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(b) Which graph, 1 to 4, shows the results of the experiment in which the acid had the highesttemperature?

Experiment ................................................

Explain fully how you know.

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

.....................................................................................................................................(

(c) (i) In experiment 2, how does the rate of reaction after one minute compare with the rate ofreaction after two minutes?

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

...........................................................................................................................(

(ii) Explain, as fully as you can, why the reaction rate changes during experiment 2.

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

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

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

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

((Total 7 mark


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M1. (a) any two from:

• increases

owtte allow ‘goes up’

• until reaches maximum / levels off

owtte

• quickly at first

owtte

• then more slowly / rate decreases

allow reaction finished

ignore rate increases2

(b) use a more concentrated acid

list principle applies

use zinc powder2

[

M2. (a) oxidising1

(b) (i) oxygen

ignore any numbers1

(ii) (catalyst) speeds up a (chemical reaction)

accept changes the rate (of reaction)

1[

M3. (a) (i) curve missing anomalous point1

(ii) answer in the range of 100.35 to 100.51

(iii) reaction goes quickly at first

accept reaction slows down1

reaction stops1

(b) because carbon dioxide is produced

accept gas is produced1

carbon dioxide / gas escapes, therefore the mass of theflask and contents decreases

1


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(c) (i) balance B1

(ii) because during the experiment a gas / carbon

dioxide escapes from the flask1

therefore the balance needs a high resolution tomeasure the small changes in the mass

1

(d) the (marble) powder has a larger surface area than the(marble) chips

1

therefore there would be more collisions with the acid particles(within the same amount of time)

1

[1

M4. (a) (i) Na2S2O3(aq) + 2 HCl(aq) → 2NaCl(aq) + H2O(l) + S(s) + SO2(g)1

(ii) (formation of) sulphuraccept precipitate or solid produced

do not accept goes cloudy or milky1

(b) (i) heat ≡ temperature increased temperature increases (the rate of reaction) or decreased temperature decreases rate of reaction

may be gained in part (ii) if stated and not implied1

(ii) (these ideas may be given in (i))

particles have more kinetic energy

accept particles move faster1

more collisions (so more reactions)

more energetic collisions two marks1

[


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M5. (a) (i) a continuous straight line missing anomalous point

allow a line which does not start at zero / origin1

(ii) any two sensible errors eg

• timing errors and / or example(*)

• measurement errors and / or example(*)

• apparatus errors and / or example(*)

• human / experimental / random error and / or exampleor ‘did not do it right’(*)

(*)could be two from same category eg two timing errors – watch notstarted at the same time plus difficulty in deciding when the cross hasdisappeared.

• temperature fluctuation

• anomalous point

accept outlier / wrong result

• results not recorded correctly

• plotting error

• rate calculated incorrectly

ignore ‘not repeated’

ignore systematic / zero error / weighing error or error unqualified2

(b) (i) straight line

or

as concentration increases the rate goes up or converse

accept numerical example

accept positive correlation

accept same gradient

ignore ‘most points near / on line of best fit’ 1

(ii) more collisions

accept greater chance of collisions

accept collide more successfully

accept alternative versions of collide eg ‘bump / hit’

ignore references to energy / speed of particles / surface area1


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more particles (in each volume of solution)(i.e. an attempt at defining concentration)

accept ‘particles are closer together’

allow ions / atoms / molecules for particles ignore reactants

accept greater frequency of collisions or greater number of collisions persecond for 2 marks

1

[

M6. (a) sensible line of best fit which goes through or close to all the points except

the anomalous point1

(b) loss of gas / loss of CO2

idea of gas produced / formed1

(c) 71

(d) (i) steeper line from around the same starting point

and left of the points

allow crosses if they are fully correct for 1 mark1

levelling off at 99

accept short level line at 99

± ½ square1

(ii) any three from:

• particles / molecules / atoms/ ions have more energy

allow given / gain / get energy

• move faster

ignore move about more

ignore vibrate more / faster

• collide more often

or more chance of collisions

or bump into each other more

ignore collide quicker / faster

• collide with more force / energy

or more particles have the activation energy

or more collisions result in reaction

or more collisions are successful3

[


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M7. (a) (must be possible for the gas to enter and displace the water) or other suitable apparatus

• apparatus to collect the gas correctly assembled

for 1 mark

• calibrated collection vessel (award even if diagram is wrong)

for 1 mark2

(b) (i) at the start / in the first 1/2 minutes (or any time within this range)for 1 mark

1

(ii) increase the temperature / use smaller pieces of metal /use more metal / increase the surface area of the metal /add a catalyst / shake the flask / increase the concentration /strength of the acid

for 1 mark1

(c) (i) 48

for 1 mark1

(ii) increase the amount of magnesium used

for 1 mark(do not allow increase the amount of acid used)

1

[

M8. (a) increase concentration of acid;increase surface area of solidor grind up the solid;

add a catalystany two for 1 mark each

2

(b) 1;it is the one that makes the gas fastest (steeper curve etc)(second part is dependant on first)

for 1 mark each2

(c) (i) faster after one minute, slower after 2 minutes

for 1 mark

1

(ii) the reactants get used up;so concentration decreases/less chance of collision

for 1 mark each2

[


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C2.5 Exothermic and endothermic reactions Revision Foundation

Q1. Distress flares are used to attract attention in an emergency.

Flares often contain magnesium. Magnesium burns to form magnesium oxide.

(a) The distress flare burns with a bright flame because the reaction is very exothermic .

Complete the following sentence using the correct words from the box.

gives out heat stores heat takes in heat

An exothermic reaction is one which ..........................................................................(

(b) Indigestion tablets can be made from magnesium oxide. The magnesium oxide neutralisessome of the hydrochloric acid in the stomach.

Draw a ring around the name of the salt formed when magnesium oxide reacts with hydrochloricacid.

magnesium chloride magnesium hydroxide magnesium sulfate(

Q2. An indigestion tablet contains sodium hydrogencarbonate and citric acid.

When the tablet is added to cold water a chemical reaction takes place and there is a lot of fizzing.

(a) The formula of the gas that causes the fizzing is CO2

Name this gas ......................................................................... .(


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(b) This chemical reaction is endothermic.

(i) Tick ( ) the statement which describes what happens to the temperature of the solution.

Statement Tick ( )

The temperature of the solution will increase.

The temperature of the solution will decrease.

The temperature of the solution will stay the same.

(

(ii) Tick ( ) the statement which describes what happens to the energy during the reaction.

Statement Tick ( )

Energy is given out to the surroundings.

Energy is taken in from the surroundings.

No energy is given out to or taken from the surroundings.

(

Q3. Instant cold packs are used to treat sports injuries.

One type of cold pack has a plastic bag containing water. Inside this bag is a smaller bag containingammonium nitrate. The outer bag is squeezed so that the inner bag bursts. The pack is shaken andquickly gets very cold as the ammonium nitrate dissolves in the water.

(a) One of the statements in the table is correct.

Put a tick ( ) next to the correct statement.

Statement ( )

The bag gets cold because heat energy is given out to the surroundings.

The bag gets cold because heat energy is taken in from the surroundings.

The bag gets cold because plastic is a good insulator.

(


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(b) Draw a ring around the word that best describes the change when ammonium nitrate dissolvesin water.

electrolysis endothermic exothermic(

(c) Suggest and explain why the pack is shaken after the inner bag has burst.

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

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

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

.....................................................................................................................................(

(Total 4 mark

Q4. The diagram shows some magnesium ribbon burning.

(a) Choose words from the list to complete the sentences below.

electrical heat light kinetic

an endothermic an exothermic a neutralisation a reduction

When magnesium burns, it transfers .........................................................................

and ............................................................................ energy to the surroundings.

We say that it is .................................................................................. reaction.(

(b) Complete the word equation for the reaction.

magnesium + __________________________ magnesium oxide(

(Total 4 mark


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Q5. The diagram shows the apparatus for an experiment. Hydrated copper sulphate crystals wereheated. They became anhydrous copper sulphate.

(a) Name a suitable piece of equipment to heat tube A.

.....................................................................................................................................(

(b) Use words from the box to complete the two spaces in the table. You may use each word onceor not at all.

black blue orange red purple white

Name Colour

Hydrated copper sulphate crystals ...................................................

Anhydrous copper sulphate ....................................................

(

(c) What is the purpose of the ice and water in the beaker?

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

.....................................................................................................................................(


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(d) Drops of a clear, colourless liquid formed on the inside of tube B.

(i) Name the liquid.

...........................................................................................................................(

(ii) Explain how the liquid came to be inside tube B.

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

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

...........................................................................................................................(

(e) Anhydrous copper sulphate can be turned into hydrated copper sulphate. What would you needto add? Apart from the change in colour, what could you observe?

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

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

.....................................................................................................................................(

(f) Copper sulphate can be made from black copper oxide by reacting it with an acid. Name theacid.

.....................................................................................................................................(

(Total 10 mark

Q6. A student did two experiments using ammonium chloride.

(a) In the first experiment the student heated a small amount of ammonium chloride in a test tube.


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Two reactions take place in the test tube.

Reaction 1 ammonium chloride → ammonia + hydrogen chloride (colourless gases)

Reaction 2 ammonia + hydrogen chloride → ammonium chloride

(i) Complete the sentences by crossing out the incorrect word in each box.

Reaction 1 takes place at a highlow

temperature.

Reaction 2 takes place at a highlow

temperature.

(

(ii) Draw a ring around the word which best describes reactions 1 and 2.

combustion displacement oxidation reduction reversible(

(iii) Suggest a reason for the mineral wool at the top of the test tube.

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

...........................................................................................................................(

(b) In the second experiment the student mixed a small amount of ammonium chloride with somewater in a beaker.

The temperature of the water was measured before and after adding the ammonium chloride.

Temperature beforeadding the ammonium

chloride

20°C

Temperature after addingthe ammonium chloride

16°C

Draw a ring around the word which best describes the process which takes place.

combustion displacement endothermic exothermic freezing(

(Total 4 mark


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M1. (a) gives out (heat)1

(b) magnesium chloride1

[

M2. (a) carbon dioxidemust be name

do not accept carbon oxide1

(b) (i) the temperature of the solution will decrease

(list principle)1

(ii) energy is taken in from the surroundings

(list principle)1

[

M3. (a) the bag gets cold because heat energy is taken in from the surroundings1

(b) endothermic1

(c) any two from:

• mix / spread (the ammonium nitrate and water)

• dissolve faster(*)

• get cold faster or so the whole bag gets cold(*)

(*)allow increase rate or quicker reaction

• particles collide more or more collisions2

[

M4. (a) heatlightan exothermic

in any order for 1 mark each3

(b) oxygen / O2

for 1 mark1

[


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M5. (a) Bunsen (burner)

accept spirit burner do not credit candle1

(b) blue 1

white

credit (1) if both colours correct but answers are reversed1

to cool the tube (B)

accept answers which anticipate part (d) e.g. ‘to condense the watervapour’ or gases or vapours

1

(d) (i) water

do not credit ‘condensation’ 1

(ii) (Water) vapour from the crystals (from tube A)

accept steam or steam from tube A1

condenses or cools

accept turns to (liquid) water1

(e) add water

gets hot or hotter or warm or warmer turns into solutiondissolves

or the temperature rises or there is an exothermic reactionaccept steams or hisses ignore any reference to colour(s)

2

(f) sulphuric acid

accept H 2 S0 4 only if correct in everydetail

1

[1

M6. (a) (i) high and low

both needed for mark1

(ii) reversible1

(iii) to prevent ammonium chloride / solid / particles escaping

idea of a filterdo not accept ‘to prevent gases escaping’

1

(b) endothermic1

[


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C2.6 Acids, bases and salts Revision Foundation

Q1. (a) The diagram shows one way of making crystals of copper sulphate.

(i) Why was the solution filtered?

..........................................................................................................................(

(ii) How could you make the crystals form faster from the copper sulphate solution?

..........................................................................................................................(

(iii) The chemical equation is shown for this reaction.

CuO(s) + H2SO4(aq) → CuSO4(aq) + H2O(l)

In the chemical equation what does (aq) mean?

..........................................................................................................................(

(b) Blue copper sulphate crystals go white when warmed. How could you use the white coppersulphate as a test for water?

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

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

....................................................................................................................................(

(Total 5 mark


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Q2. A solution of Y was slowly added to a solution of X. The graph shows how the pH of the resultingsolution changed.

(a) (i) What was the pH of solution X before any of solution Y was added?

...........................................................................................................................(

(ii) State whether solution Y was acidic, alkaline or neutral.

...........................................................................................................................(

(iii) What volume of solution Y was needed to react with all of the substance in solution X?

.................................................................................................................... cm3

(

(b) The chemical equation shows the reaction between an acid and an alkali to form a salt andwater.

(i) Draw a circle round the formula of the alkali.

H2SO4 + 2KOH → K2SO4 + 2H2O(

(ii) What is the formula of the salt?

...........................................................................................................................(

(Total 5 mark


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Q3. Salts can be prepared by the reaction of acids with alkalis.

(a) (i) The reactions of acids with alkalis can be represented by the equation below. Choose asubstance from the box to complete the equation.

carbon dioxide hydrogen oxygen water

acid + alkali → salt + ..........................................................(

(ii) Draw a ring around the word which best describes the reaction.

displacement neutralisation oxidation reduction(

(b) Sodium sulphate is an important salt. The table gives a list of some substances.

Put a tick ( ) next to the names of the acid and the alkali that would react to make sodiumsulphate.

Substances ( )

Hydrochloric acid

Nitric acid

Potassium sulphate

Sodium hydroxide

Sodium nitrate

Sulphuric acid

(

Q4. (a) Citric acid produces hydrogen ions in aqueous solution. These ions can be represented asH+(aq). Complete this sentence.

The (aq) means that the acid has been dissolved in .................................................. .

(

(c) Citric acid is a weak acid. Draw a ring around the correct answer to complete the sentence.

has a low boiling point.

The word weak means that the acid is dilute.

is partially ionised in water.

(


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(d) A student measured the pH of four acids, A, B, C and D.

The acids were the same concentration. The same quantity of magnesium ribbon was added toeach of the acids. The volume of gas produced after 5 minutes was recorded.

The results are shown in the table.

Acid pH Volume of gas in cm3

A 2 18

B 5 6

C 1 24

D 4 12

(i) State one way in which the student made sure that the experiment was fair.

...........................................................................................................................(

(ii) Use the results to arrange the acids, A, B, C and D in order of decreasing acid strength.

Most acidic ........................................................................................ Least acidic.(

(e) When acids react with alkalis, the hydrogen ions from the acid react with the hydroxide ions from

the alkali.

(i) Which one of the following represents the formula of a hydroxide ion?

Draw a ring around your answer.

H – O – OH –

(

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

acidic.

A solution with more hydrogen ions than hydroxide ions is alkaline.

neutral.

((Total 7 mark


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Q5. Nitric acid can be neutralised by alkalis to make salts.

(i) The salt called potassium nitrate can be made from nitric acid.

Complete the word equation for this neutralisation reaction.Choose the correct substances from the box.

hydrogen oxygen potassium chloride

potassium hydroxide water

nitric acid + ................................ →potassium nitrate + ................................ (

(ii) Ammonium nitrate is another salt made from nitric acid.

Which one of the following is the main use of ammonium nitrate? Draw a ring around your

answer.

dye fertiliser plastic fuel(

(iii) Complete this sentence by choosing the correct ion from the box.

H+ NH4+ NO3 – O2 – OH –

The ion that makes solutions acidic is ............................................................ .(

(Total 4 mark

Q6. A student tried to make some magnesium sulphate. Excess magnesium was added to dilutesulphuric acid. During this reaction fizzing was observed due to the production of a gas.

(i) Complete and balance the chemical equation for this reaction.

..................... + H2SO4 → ....................... + ........................(


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(ii) At the end of the reaction the solution remaining was filtered. Why was the solution filtered?

.....................................................................................................................................(

(iii) The filtered solution was left in a warm place.

Explain why the filtered solution was left in a warm place.

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

.....................................................................................................................................(

(Total 6 mark

Q7. Ammonium nitrate and ammonium sulphate are used as fertilisers.

(i) Which acid reacts with ammonia to form ammonium nitrate?

....................................................................................................................................(

(ii) Which acid reacts with ammonia to form ammonium sulphate?

....................................................................................................................................(

(iii) The reactions in (i) and (ii) are both exothermic. How can you tell that a reaction is exothermic?

....................................................................................................................................(

(iv) The reactions in (i) and (ii) are both examples of acid + base reactions. What is the name of thechemical change which takes place in every acid + base reaction?

....................................................................................................................................(

(Total 4 mark


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Q8. The following passage is about the preparation of lead iodide, an insoluble salt.

An excess of potassium iodide in solution was shaken withsome lead nitrate solution in a test tube.

The lead iodide precipitate was separated from the mixtureand then washed several times with water.

The lead iodide was dried and then placed in a bottle.

(a) Suggest a reason why excess potassium iodide was used.

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

.....................................................................................................................................(

(b) What word used in the passage shows that lead iodide is insoluble?

....................................................................................................................................(

(c) Suggest how lead iodide can be separated from the mixture.

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

....................................................................................................................................(

(d) Why was the lead iodide washed with water?

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

....................................................................................................................................(

(e) Suggest a method which could be used to dry this lead iodide.

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

....................................................................................................................................(

(f) Lead compounds are toxic.

Suggest a suitable safety precaution that should be taken when using toxic substances inlaboratories.

....................................................................................................................................(

(Total 6 mark


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Q9. The diagrams show what happens when an acid is added to an alkali.

(a) What is present in the flask at stage 2, besides universal indicator and water?

.....................................................................................................................................(

(b) Write an ionic equation to show how water is formed in this reaction and state the sources of theions.

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

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

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

.....................................................................................................................................(

(Total 4 mark


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M1. (a) (i) to remove or separate copper oxide

accept to remove or separate

unreacted or excess base

accept to remove or separate insoluble solids1

(ii) heat (the solution)

accept heat the water

accept evaporate the water

rapid cooling/cool to lower temperature

accept boil the water or solution

not increase surface area, put in

draught

not increase the temperature1

(iii) aqueous

accept in water

accept solution

not soluble in water1

(b) add water/liquid/solution1

colour changes to blue1

[

M2. (a) (i) allow a number between 2.5 and 3(inclusive)

accept just under 3 or about 31

(ii) alkaline or alkali1

(iii) 25

ignore any reference to units1

(b) (i) a circle round KOH or 2 KOH1

(ii) K2SO4

do not credit potassium sulphate1

[


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M3. (a) (i) water

accept H 2 Oaccept correct ringed answer in box

1

(ii) neutralisation

accept underlining or any indication, eg tick

1

(b) sodium hydroxide1

sulphuric acid

apply list principletotal1

[

M4. (a) water / H2O / hydrogen oxide1

(b) is partially ionised in water1

(d) (i) eg same concentration / quantity of Mg

accept: volume of acid / ribbon for both / same time

accept: volume of gas measured under the same conditions1

(ii) C A D B1

(e) (i) OH –

1

(ii) acidic1

[

M5. (i) potassium hydroxide

accept correct formulae1

water1

(ii) fertiliser1

(iii) H+

accept hydrogen but not H1

[


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(iii) heat given out

or temperature rise

or energy given out

or steam

do not credit just ‘use a thermometer’

do not credit just 'change in temperature'1

(iv) neutralisation

accept neutralise

accept neutral

accept formation of salt or water

do not credit exothermic1

[

M8. (a) all lead nitrate reactedor no lead nitrate leftor enough KI to react with lead nitrate

or to remove all the lead ionsor to get maximum amount of I2

ignore comments about speeddo not accept to remove all the lead

1

(b) precipitate

allow phonetic spellingdo not accept ppt

1

1

(c) filter / filtration / centrifuge / decant

do not accept sieve

(d) any one from:

• removes (soluble) impurities


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• removes (unreacted) KI

• removes KNO3

• removes (excess) solution

• removes nitrates

purifying is insufficientdo not accept removes potassium

do not accept removes iodide 1

(e) answer based on filter paper, desiccator, suitable solvent(gentle) heat, drying cabinet, oven etc.

Accept any method of heating i.e.bunsen / hairdryer etc.

Accept leave to evaporate / stand or leave in a warm room

e.g. place between dry filter paper, allow to dry

e.g. use propanone, allow to drye.g. leave on sunny window sille.g. leave in a draught

the answer leave / evaporate /

draught alone is insufficient1

(f) wear gloves / maskor fume-cupboard

or wash hands afterwardsignore goggles / labcoat or extractor fan / do not touch etc.

1

[6]

M9.

(a) sodium ions and chloride ions (not chlorine)allow sodium chloride/salt/common salt

for 1 mark1

(b) H+ + OH – →H2OH+ from (hydrochloric) acidOH- from alkali/sodium hydroxidelose 1 mark if no charge shown disregard other ions

each for 1 mark3

[


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C2.7 Electrolysis Revision Foundation

Q1. The electrolysis of sodium chloride solution produces useful substances.

(a) (i) Choose a word from the box to complete the sentence.

covalent ionic non-metallic

Electrolysis takes place when electricity passes through ..................................

compounds when they are molten or in solution.(

(ii) Choose a word from the box to complete the sentence.

alkenes elements salts

During electrolysis the compound is broken down to form...............................(

(b) The diagram shows an apparatus used for the electrolysis of sodium chloride solution.

Identify the products A, B and C on the diagram using substances from the box.

chlorine gas hydrogen gas oxygen gas

sodium hydroxide solution sodium metal

(i) A is ....................................................................................................................(

(ii) B is ....................................................................................................................(

(iii) C is ....................................................................................................................(

(Total 5 mark


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Q2. A student investigated the electrolysis of lead bromide.

Lead bromide was placed in the tube and the circuit was switched on. The light bulb did not light up.

The tube was heated and soon the bulb lit up. The observations are shown in the table.

Positive electrode Negative electrode

red-brown gas silver liquid

(a) What is meant by electrolysis?

....................................................................................................................................(

(b) Why did the lead bromide conduct electricity when the tube was heated?

....................................................................................................................................(

(c) Name the substances formed at the:

positive electrode; .....................................................................................................

negative electrode. .................................................................................................... (

(d) Suggest one safety precaution that should be taken during this investigation.

....................................................................................................................................(

(Total 6 mark


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Q3. Electrolysis can be used to remove unwanted hair from the skin.

The positive electrode is connected by a patch to the skin.

The negative electrode is connected to the hair.

The body fluid is a solution that contains sodium chloride. The electricity causes theelectrolysis of a small amount of this solution.

(a) In this solution hydrogen ions move to the negative electrode.

Complete the sentence using one word from the box.

negative neutral positive

Hydrogen ions move to the negative electrode because they have a

....................................................... charge.

(

(b) Draw a ring around the name of the gas produced at the positive electrode during theelectrolysis of sodium chloride solution.

chlorine hydrogen nitrogen(

(c) The electrolysis of the sodium chloride solution forms a strong alkali around the hair follicle.

(i) Complete the name of this strong alkali using one of the words from the box.

chlorine hydrogen nitrogen

The name of this strong alkali is sodium ............................................ .(

(ii) Suggest how this strong alkali helps to remove the hair.

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

...........................................................................................................................(

(Total 4 mark


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Q4. The electrolysis of sodium chloride solution is an important industrial process. The apparatusshown below can be used to show this electrolysis in the laboratory.

(a) Name gas A. ...............................................................................................................(

(b) Chlorine is produced at the positive electrode. Describe and give the result of a chemical test toprove that the gas is chlorine.

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

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

.....................................................................................................................................(

(c) Chloride ions move to the positive electrode. Explain why.

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

.....................................................................................................................................(

(d) A small quantity of chlorine is added to drinking water. Explain why.

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

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

(

(e) The solution around the negative electrode becomes alkaline. Name the ion which makes thesolution alkaline.

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

.....................................................................................................................................(

(Total 6 mark


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Q5. Read the information in the box and then answer the question.

Aluminium is made by the electrolysis of aluminium oxide.

Aluminium oxide is an ionic compound containing aluminium ions (Al3+) and oxide ions(O2 –).

The diagram below shows the apparatus used to electrolyse aluminium oxide.

(a) In this question you will get marks on using good English, organising information clearly andusing specialist terms correctly.

Use information in the box and your knowledge and understanding of this process to answer thisquestion. Explain, as fully as you can, how aluminium and carbon dioxide are formed in thisprocess.

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

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

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

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

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

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

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

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

(

(b) Explain why cryolite is added.

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

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

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

(


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M1. (a) (i) ionic1

(ii) elements1

(b) (i) chlorine (gas)

allow Cl 2 / Cl / Cl 2

allow chloride1

(ii) hydrogen (gas)

allow H / H 2 / H 2

1

(iii) sodium hydroxide (solution)

allow NaOH

allow sodium solution1

[

M2. (a) breakdown / decomposition / splits into elements /

not ions

separates into elements / produce a chemical reaction1

using electricity

1

(b) lead bromide melted / free ions

not electrolyte1

(c) (+) bromine

element must be appropriate to electrode1

( –) lead

element must be appropriate to electrode1

(d) fume cupboard / protective clothing

allow safety glassesnot safety mat

1


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[

M3. (a) positive

accept + or +ve or plus1

(b) chlorine1

(c) (i) hydroxide

Any indication of hydro… 1

(ii) destroys / damages / dissolves (owtte) the hair / follicle / root

allow burns / reacts with the hair

ignore incorrect name of compound1

[

M4. (a) hydrogen

accept H 2

do not accept H 1

(b) litmus paper / Universal Indicator paper / pH paper

allow any suitable named indicator1

bleached / turns white or loses its colour

do not accept bleached cloth / leaves etc.

allow second mark unless incorrect indicator given

allow starch iodide paper (1)

goes black / blue black (1)allow potassium iodide solution (1) goes brown / orange / black

precipitate (1)1

(c) because they have a negative charge or opposite charges attract

accept (because) it is Cl –

accept chlorine, Cl or chlorine ions has a negative charge

do not accept Cl – on its owndo not accept Cl 2 o.e. has negative charge

1

(d) kill bacteria / germs, etc. or sterilise / disinfect

accept destroys bacteria etc.ignore clean / purify water (owtte)do not accept just gets rid of bacteria

1

(e) hydroxide (ion)

accept OH –

1

[


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M5. (a) Marks awarded for this answer will be determined by the Qualityof Written Communication (QWC) as well as the standard of thescientific response.

No relevant content.0 marks

There is a brief description of the electrolysis of aluminium oxide.Level 1 (1

– 2 marks)

There is some description of the electrolysis of aluminium oxide.Level 2 (3 – 4 marks)

There is a clear, balanced and detailed description of theelectrolysis of aluminium oxide.

Level 3 (5 – 6 marks)

examples of the chemistry points made in the response

• aluminium oxide is melted / made liquid

• aluminium ions are attracted to the negative electrode

• at the negative electrode aluminium is formed oraluminium ions gain electrons

• oxide ions are attracted to the positive electrode

• oxygen is formed at the positive electrode or oxideions lose electrons

• the oxygen reacts with carbon to make carbon dioxide orcarbon dioxide formed at positive electrode.

(b) Lowers melting point 1.

Less energy/electricity needed 1

Saves money 1

c2 foundation revision questions - sets 3,4&5

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