A Level Initial Assessment

These are high demand GCSE questions based upon topics you studied in KS4 and will need to know about in your A Level course.

16/09/2011

60 minutes

64 marks

Page 1 of 20

Q1. Sodium reacts with chlorine to form the compound sodium chloride.

2Na + Cl2 →  2NaCl

Describe, in terms of electron arrangement, the type of bonding in:

(i) a molecule of chlorine;

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(ii) the compound sodium chloride.

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(Total 7 marks)

Q2. Fluorine is the most reactive element in group 7 of the Periodic Table. Fluorine reacts with all the other elements in the Periodic Table except some of the noble gases. It does not react with helium, neon and argon, but it does react with xenon. Many substances burst into flames when exposed to fluorine.

(a) (i) The electronic structure of chlorine is 2.8.7. What is the electronic structure of fluorine?

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(ii) What is the electronic structure of the chloride ion Cl–?

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(iii) Explain why fluorine is more reactive than chlorine.

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(b) (i) What does the information at the start of this question suggest about the reactivity of the elements in group 0?

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(ii) A chemist did an experiment to find out if fluorine reacts with xenon. The two gases were mixed in a glass container. The only product detected was silicon fluoride. Explain what happened.

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(iii) The experiment was repeated many years later but the gases were mixed in a different type of container. A white solid was obtained which was xenon fluoride.

Predict whether you think (1) krypton and (2) radon will react with fluorine. Explain the reasons for your predictions.

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(Total 14 marks)

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Q3.

(i) Describe the structure and bonding in metals. Draw a diagram to help if you wish

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(ii) Explain why metals such as nickel and platinum are good conductors of electricity.

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(Total 13 marks)

Q4. At room temperature, hydrogen peroxide decomposes very slowly to form water and oxygen. The decomposition is speeded up when a catalyst is added.

(a) The following equation represents the decomposition of hydrogen peroxide. The structural formulae of the chemicals involved are shown.

Use the following information about bond energies to answer this part of the question.

BOND BOND ENERGY (kJ)

O = O 498

O – O 146

H – O 464

(i) Calculate the energy needed to break all the bonds in the reactants.

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

(ii) Calculate the energy released when new bonds are formed in the products.

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

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(iii) Calculate the energy change for this reaction.

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

(iv) Is the reaction exothermic or endothermic?

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Explain why.

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(b) (i) What is meant by ‘activation energy’?

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(ii) The energy level diagram for the decomposition of hydrogen peroxide into water and oxygen is shown below.

Which energy change, A, B, C or D, is the activation energy? ....................... (1)

(iii) Explain, in terms of energy, how a catalyst makes hydrogen peroxide decompose more quickly.

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(Total 9 marks)

(b) Uranium has two main isotopes, and . Use these as examples to explain what is meant by the word isotope.

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Page 6 of 20

Q5. Uranium metal can be produced by reacting uranium hexafluoride with calcium.

UF6 +  3Ca  →  3CaF

2 +  U

(a) Describe how calcium and fluorine bond together to form calcium fluoride. The electron arrangement of each atom is shown.

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(c) At the start of a reaction there was 174.5 g of uranium hexafluoride, UF6.

Relative atomic masses: F 19; U 235

(i) Calculate the relative formula mass of uranium hexafluoride, UF6.

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Relative formula mass UF6 = .................................... g

(1)

(ii) Calculate the mass of uranium that would be produced from 134.5 g of uranium hexafluoride.

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Mass of uranium = .................................. g (2)

(Total 12 marks)

Q6. The balanced symbol equation for the reaction is

H2 (g) + Cl

2 (g)  →  2HCl (g)

Starting with 2 g of hydrogen, what mass of hydrogen chloride would be produced? (Relative atomic masses: H = 1; Cl = 35.5)

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Mass of hydrogen chloride = ...................................... g (Total 3 marks)

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Q7. Petrol is a mixture of hydrocarbons such as octane, C8H

18

When petrol is burned in a car engine, a large amount of carbon dioxide is produced.

This car uses 114 g of petrol to travel one mile.

Calculate the mass of carbon dioxide produced when this car travels one mile.

Assume that petrol is octane and that combustion is complete.

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

The combustion of octane can be represented by this equation.

C8H

18 + 12 O

2 → 8CO

2 + 9H

2O

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Mass of carbon dioxide = ........................ g (Total 3 marks)

Q8. Iron is the most commonly used metal. Iron is extracted in a blast furnace from iron oxide using carbon monoxide.

Fe2O

3 +  3CO  →  Fe  +  3CO

2

(a) A sample of the ore haematite contains 70% iron oxide.

Calculate the amount of iron oxide in 2000 tonnes of haematite.

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Amount of iron oxide = ......................................... tonnes (1)

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(b) Calculate the amount of iron that can be extracted from 2000 tonnes of haematite. (Relative atomic masses: O = 16; Fe = 56)

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Amount of iron = .................................................... tonnes (4)

(Total 5 marks)

Q9. Aspirin tablets have important medical uses.

A student carried out an experiment to make aspirin. The method is given below.

1. Weigh 2.00 g of salicylic acid. 2. Add 4 cm3 of ethanoic anhydride (an excess). 3. Add 5 drops of concentrated sulfuric acid. 4. Warm the mixture for 15 minutes. 5. Add ice cold water to remove the excess ethanoic anhydride. 6. Cool the mixture until a precipitate of aspirin is formed. 7. Collect the precipitate and wash it with cold water. 8. The precipitate of aspirin is dried and weighed.

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(a) The equation for this reaction is shown below.

C7H

6O

3 + C

4H

6O

3   →   C

9H

8O

4 + CH

3COOH

salicylic acid aspirin

Calculate the maximum mass of aspirin that could be made from 2.00 g of salicylic acid.

The relative formula mass (Mr) of salicylic acid, C

7H

6O

3, is 138

The relative formula mass (Mr) of aspirin, C

9H

8O

4, is 180

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Maximum mass of aspirin = .............................. g (2)

(b) The student made 1.10 g of aspirin from 2.00 g of salicylic acid.

Calculate the percentage yield of aspirin for this experiment.

(If you did not answer part (a), assume that the maximum mass of aspirin that can be made from 2.00 g of salicylic acid is 2.50 g. This is not the correct answer to part (a).)

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Percentage yield of aspirin = .............................. % (2)

(c) Suggest one possible reason why this method does not give the maximum amount of aspirin.

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(d) Concentrated sulfuric acid is a catalyst in this reaction.

Suggest how the use of a catalyst might reduce costs in the industrial production of aspirin.

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(Total 6 marks)

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M1. (i) can be from diagram chlorine (2.8).7. accept chlorine needs one more electron

1

can be from diagram shares a pair of electrons 1

shared pair of electrons is a covalent bond do not accept ionic bond

1

(ii) can be from diagram and appropriately annotated sodium (2.8). 1. and chlorine (2.8).7

1

sodium loses one electron and chlorine gains one electron 1

Na+ and Cl– formed

1

bond formed between oppositely charged ions or ionic bond is formed do not accept covalent bond

1 [7]

M2. (a) (i) 2.7 1

(ii) 2.8.8 1

(iii) gains an electron more easily than Cl because the higher the energy level the less easily an electron is gained

each for 1 mark 4

(b) (i) very unreactive or give reactivity trend 1

(ii) fluorine reacted with silicon from glass each for 1 mark

2

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(iii) Reactivity increases down the group radon likely to react because lower in group than xenon more reactive than xenon Kr may or may not react higher in group than xenon less reactive than xenon

any 5 for 1 mark each 5

[14]

M3.

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(a) (i) giant structure/lattice/regular arrangements of atoms any for 1 mark

of atoms/of ions (provided free electrons mentioned) either for 1 mark

delocalised or free electrons for 1 mark

3

(ii) electrons free/can move for 1 mark each

2 [13]

M4. (a) (i) 4 E (H-O) = 4 × 464 = 1856 2 E (O-O) = 2 × l46 = 292

gains 1 mark each

but Total = 2148 kJ Deduct one mark for each mistake. Answer of 1074 kJ gains 1 mark. (Candidate has ignored the 2 in front of the brackets.)

gains 2 marks 2

(ii) 4 E (H-O) = 4 × 464 = 1856 E (O=O) = 498

gains 1 mark each

but Total = 2354 kJ Deduct one mark for each mistake. Answer of 1426 kJ gains 1 mark. (Candidate has ignored the 2 in front of the brackets.)

gains 2 marks 2

(iii) 2354 – 2148 = 206 kJ (Ignore any signs) Answer is consequential on their answers to (i) and (ii).

for 1 mark 1

(iv) exothermic because (more) heat is given out (than put it) / or ΔH is negative /answer to (iii) is negative.). (If the candidate gives the answer ‘endothermic because heat /energy is taken in’ then look back to their answers to (i) and (ii). If (i) is greater than (ii) then accept this answer.

for 1 mark 1

(b) (i) eg minimum energy for reaction energy needed to start a reaction energy needed to break bonds energy needed to make two substances react (Energy linked to starting a reaction.)

for 1 mark 1

(ii) B for 1 mark

1

(iii) lowers activation energy / needs less energy to start reaction / less energetic route

for 1 mark 1

[9]

M5. (a) calcium atom loses two electrons accept diagrams with correct labelling

1

(each) fluorine atom gains one electron accept two electrons transfer from a calcium atom to the two fluorine atoms for these first two marks

1

forming full (outer) shells of electrons accept forming full (outer) energy levels or noble gas electronic structures do not accept stable unless qualified

1

giving the ions Ca2+ and F−

1

attraction between ions of opposite charges accept electrostatic attraction between ions if candidate mentions sharing or pairing of electrons then no credit if explanation is entirely correct but they state this is called covalent bonding, the maximum mark is four

1

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(b) atoms of the same element 1

atomic number is same accept each contains 92 or same number of protons

1

mass numbers differ or each has a different number of neutrons 1

one has 146 neutrons the other has 143 neutrons accept one has three more or less neutrons than the other

1

(c) (i) 349 1

(ii) 349g UF2 produces 235g U [1]

first mark can be awarded if answer is incorrect

answer = 117.5 1

[12]

M6. 73 (seventy three) if answer is incorrect allow 1 mark for the correct proportion that H

2:HCl is 1:2

and 1 mark for 36.5 [3]

M7. 352 g gains 3 marks

(moles C8H

18 = 114 / 114 = 1 mole)

moles CO2 = 8 (1)

mass CO2 = 8 × 44 (1) = 352 g (1)

1 mark for each point (ecf allowed between parts)

or

114 → 8 (1) × 44 (1)

114   →   352 g (1)

ecf allowed between parts [3]

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M8. (a) 1400 1

(b) 980 correct answer gains full credit

160 tonnes Fe2O

3 produces 112 tonnes Fe

if incorrect allow one mark for relative formula mass iron oxide = 160 allow e.c.f.

1400 tonnes Fe2O

3 will produce 1400 / 160 × 112 tonnes Fe

use of 2000 tonnes Fe2O

3 – deduct one mark only if

working out is correct 4

[5]

M9. (a) 2.61 / range 2.5 to 2.7 correct answer with or without or with wrong working gains 2 marks (accept answers between 2.5 and 2.7) if answer incorrect moles of salicylic acid = 2/138 = 0.0145 moles ie 2/138 or 0.0145 gains 1 mark or (180/138) × 2 gains 1 mark or 1 g → 180/138 = (1.304 g) gains 1 mark (not 1.304g alone)

2

(b) 42.1 range 40.7 to 42.3 accept correct answer with or without or with wrong working for 2 marks ecf ie (1.1 / their answer from (a)) × 100 correctly calculated gains 2 marks if answer incorrect percentage yield = 1.1 / 2.61 × 100 gains 1 mark

if they do not have an answer to part (a) or they choose not to use their answer then:

• yield = (1.1 / 2.5) × 100 (1)

• = 44 accept 44 for 2 marks with no working

2

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(c) any one from:

• errors in weighing

• some (of the aspirin) lost do not allow ‘lost as a gas’

• not all of the reactant may have been converted to product eg reaction didn’t go to completion allow loss of some reactants

• the reaction is reversible accept other products / chemicals

• side reactions ignore waste products

• reactants impure

• not heated for long enough

• not hot enough for reaction to take place 1

(d) any one from:

• use lower temperature

• use less fuel / energy ignore references to use of catalyst

• produce product faster or speed up reaction

• more product produced in a given time (owtte)

• increased productivity

• lowers activation energy 1

[6]

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