1. The diagram shows electrolysis of sodium chloride solution.

(a) Complete and balance these equations to show the reactions during electrolysis.

At the positive electrode

Cl– – e– Cl2

At the negative electrode

Na Na(2)

(b) Silver halides such as silver chloride and silver bromide are used in photography.The equation shows a reaction to prepare a silver halide.

Name and describe the products of this reaction, in words, as fully as you can.

product 1

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product 2

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(Total 6 marks)

Keswick School 1

c h lo rin e g as

p o s itiv ee lec tro d e (c a rb o n )

p o w er su p p ly

n eg a tiv ee lec tro d e (carb on )

h y d ro g e n g as

so diu m c h lo r id eso lu tio n

c h lo rin e g as

p o s itiv ee lec tro d e (c a rb o n )

p o w er su p p ly

n eg a tiv ee lec tro d e (carb on )

h y d ro g e n g as

so diu m c h lo r id eso lu tio n

3(aq)(s)3(aq)(aq) NaNOAgBrAgNONaBr

2product1productreactants

2. Read the passage carefully and then answer the questions.

The electrolysis of acidified water

After a few drops of dilute sulphuric acid have been added to some distilled water, there will be three types of ion in solution:

from the water, H2O(l) H+(aq) + OH–(aq)

from the acid, H2SO4(aq) 2H+(aq) + SO42– (aq)

When the electrodes (anode and cathode) in a circuit are put into the acidified water, the hydroxide ions and the sulphate ions are both attracted to the electrode called the anode. However, it is harder for the sulphate ions to give up their electrons than for the hydroxide ions to do this. So the hydroxide ions are the ones which react and bubbles of oxygen are formed at the anode.

There are only hydrogen ions to be attracted towards the cathode and, when they get there, they take up electrons to form hydrogen molecules.

From Chemistry Matters by Richard Hart, reproduced by permission of Oxford University Press

Even in a small volume of water acidified with dilute sulphuric acid there will be billions of ions. Some will be anions and some will be cations.

(i) Name the ions in water acidified with dilute sulphuric acid.

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(ii) Explain why only some of the ions are attracted to the anode.

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(iii) Balance the equation for the reaction of hydroxide ions at the anode.

4OH– H2O + O2 + e–

(1)(Total 4 marks)

Keswick School 2

3. Read the article and then answer the questions that follow.

Hydrogen fuel for cars?

Hydrogen is an excellent fuel. It can be made by the electrolysis of potassium hydroxide solution.

Hydrogen gas can be stored under pressure in a cylinder but a leak of the gas could cause an explosion.

It has been found that lithium nitride can absorb and then release large volumes of hydrogen. A chemical reaction takes place between the hydrogen and the lithium nitride. The hydrogen is held in the resulting compounds by chemical bonds.

The problem is that the rate at which hydrogen is absorbed and then released from normal sized particles of lithium nitride is slow.

Recently scientists have made ‘nanosized’ particles of lithium nitride. These particles absorb hydrogen in the same way as normal sized lithium nitride particles. The ‘nanosized’ particles have the advantage that they absorb and release the hydrogen much faster when needed in the fuel cell.

It is hoped that ‘nanosized’ particles of lithium nitride may provide a safe method of storing hydrogen in the future.

(a) Hydrogen is produced at the negative electrode during the electrolysis of potassium hydroxide solution.

(i) Why are hydrogen ions attracted to the negative electrode?

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(ii) Potassium ions are also attracted to the negative electrode.

Explain why hydrogen gas is formed but not potassium.

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Keswick School 3

(b) Lithium nitride is made by reacting lithium with nitrogen.

Balance the equation for this reaction.

.......... Li + N2 → .......... Li3N(1)

(c) (i) The equation for the reaction of lithium nitride with hydrogen is:

Li3N + 2H2 LiNH2 + 2LiH

What feature of this reaction allows the hydrogen to be released?

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(ii) Hydrogen stored in a fuel tank filled with lithium nitride would be safer in an accident than a cylinder full of hydrogen.

Suggest and explain why.

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(d) (i) State how ‘nanosized’ particles will be different from normal sized particles of lithium nitride.

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(ii) Suggest why the ‘nanosized’ particles of lithium nitride absorb and release the hydrogen more quickly than normal sized particles.

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Keswick School 4

(e) Lithium nitride is an ionic compound which contains lithium ions (Li+) and nitride ions

(N3–).

(i) The formation of a lithium ion from a lithium atom is an oxidation reaction.

Explain why.

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(ii) The diagram shows the electronic structure of a nitrogen atom.

Complete the diagram below to show the electronic structure of a nitride ion (N3–).

(1)(Total 10 marks)

4. (a) By reference to their structure, explain how the particles in a piece of metal are held together and how the shape of the metal can be changed without it breaking.

(You may use a diagram in your answer.)

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Keswick School 5

(b) Explain why metals are good conductors of electricity and suggest why this conductivity increases across the periodic table from sodium to magnesium to aluminium.

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(Total 9 marks)

5. The diagram shows a model of part of the giant lattice of a metal.

(a) Name particles X and Y.

X .....................................................

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

Keswick School 6

X

Y

(b) Explain, in terms of the giant structure above, why is it possible to bend a piece of metal.

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(Total 4 marks)

6. (a) The formula for the chemical compound magnesium sulphate is MgSO4.

Calculate the relative formula mass (Mr)of this compound. (Show your working.)

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(b) Magnesium sulphate can be made from magnesium and dilute sulphuric acid.

This is the equation for the reaction.

Mg + H2SO4 MgSO4 + H2

Calculate the mass of magnesium sulphate that would be obtained from 4g of magnesium.(Show your working.)

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Answer..................................... g(2)

(Total 4 marks)

Keswick School 7

7. Epoxyethane has the formula C2H4O. It is used to make antifreeze and some types of plastic.

When choosing a method of making a chemical, it is important to consider:

the percentage yield the atom economy.

Epoxyethane can be made from ethene by two different methods. The overall equation for each method is shown below.

Method 1

C2H4 + Cl2 + Ca(OH)2 C2H4O + CaCl2 + H2Oethene epoxyethane

Method 2

catalyst2C2H4(g) + O2(g) 2C2H4O(g)ethene epoxyethane

The table gives the relative formula masses (Mr) of the reactants and products for Method 1.

Formula of reactant or product Relative formula mass (Mr)

H2O 18

C2H4 28

C2H4O 44

Cl2 71

Ca(OH)2 74

CaCl2 111

The percentage atom economy can be calculated using:

Percentage atom economy = 100

The percentage atom economy for Method 2 is 100.

(a) Calculate the percentage atom economy for Method 1.

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Keswick School 8

togetheradded reactants all of Total

product useful of

r

r

M

M

(b) Method 2 has the higher atom economy.

Suggest why this is an advantage.

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(c) State and explain how an increase in pressure would affect the equilibrium yield of epoxyethane using Method 2.

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(d) One problem with Method 2 is that ethene can also react with oxygen to make carbon dioxide and water.

C2H4 + 3O2 2CO2 + 2H2O

How might this reaction affect the percentage yield of epoxyethane?

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(Total 7 marks)

8. The monomer chloroethene is made from ethene in a two-stage process,

(a) The first stage is to convert ethene to 1,2-dichloroethane.

2C2H4(g) + 4HC1(g) + O2(g) 2C2H4Cl2(g) + 2H2O(g) ethene 1,2-dichloroethane

State and explain the effect of increasing the pressure on:

(i) the yield of 1,2-dichloroethane;

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Keswick School 9

(ii) the rate of reaction.

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(b) In the second stage 1,2-dichloroethane is converted into chloroethene.

C2H4C12 C2H3C1 + HCl

This reaction is a thermal decomposition.

Suggest what would need to be done to decompose 1,2-dichloroethane.

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(Total 5 marks)

9. Sodium chloride solution is a useful raw material for the manufacture of other substances.

(i) What is the name of the process shown?

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(ii) Chloride ions lose electrons at the positive electrode. What is the name of this type of reaction?

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Keswick School 10

+ –P o s itiv e

e le c tro d eN eg ativ ee le c tro d e

S o d iu m c h lo r id eso lu tio n

C h lo rin eg a s

H y d ro g enga s

X

P o ro u s m em b ran e

(iii) The solution formed at X is alkaline. What causes this solution to be alkaline?

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(iv) Give a balanced ionic equation for the formation of hydrogen gas at the negative electrode.

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(Total 7 marks)

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

The hair is first coated with a layer of gel containing ions in solution.

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

The negative electrode is connected to the hair. Electricity flows through the gel and causes electrolysis of the body fluid around the hair follicle.

(a) Metal wires conduct electricity to the electrodes.

Explain how metals conduct electricity.

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Keswick School 11

P o w er su p p ly

H air

B o d y flu id

H a ir fo llic le

P o sitiv ee lec tro d e

N eg a tiv ee lec tro d e

(b) Explain why the gel containing ions in solution can conduct electricity.

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(c) The body fluid is a solution that contains sodium chloride. The electricity causes the electrolysis of a small amount of this solution.

This solution contains hydrogen ions that move to the negative electrode.

(i) The half equation represents the reaction at the negative electrode.

2H+ + 2e– → H2

Explain why this reaction is a reduction.

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(ii) As a result of the electrolysis of sodium chloride solution, an alkali forms which kills the hair follicle.

What is the name of this alkali? .......................................................................(1)

(iii) Complete the half equation for the reaction at the positive electrode.

Cl – → Cl2(1)

(Total 6 marks)

11. Ammonia is manufactured from nitrogen and hydrogen. The reaction is shown in the equation below.

Keswick School 12

N2

nitrogen3H2

hydrogen2NH3

ammonia

exothermic

endothermic+

The diagram shows some details of the manufacturing process.

The graph shows the percentage of reacting gases converted into ammonia at different temperatures and pressures.

At room temperature and pressure, the reaction is very slow and only a small percentage of the reacting gases is converted to ammonia.

Use the information on the diagram and graph to:

Keswick School 13

n itro ge n

h y d rog e n

2 5 0a tm o sp h ere s

p ressu re

4 5 0 ºCiro n

p o w d e r m ix tu reco n ta in in g

1 5 %a m m o n ia

u n re ac tedn itro g e n

an dam m on ia

m ix tu reo f g a se s

u n de rp ressu re

R E A C T O R(re in fo rc ed

s tee l)

am m o n iaco o led to liq u id

a n d re m o v e d

c o m p resso r

7 0

6 0

5 0

4 0

3 0

2 0

1 0

00 1 0 0 2 0 0

P ressu re (a tm o sp h eres )

3 0 0 4 0 0

% o frea c tin g g asesco n v erte d in to

am m o n ia

3 5 0 ºC

4 5 0 ºC

5 5 0 ºC

(a) describe the conditions used in the manufacture of ammonia to increase the rate of reaction.

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(b) describe and explain the conditions used in the manufacture of ammonia to increase the yield.

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(Total 11 marks)

Keswick School 14

12. Read the article about the use of nanoparticles in sun creams.

Sun creams

Many sun creams use nanoparticles. These sun creams are very good at absorbing radiation, especially ultraviolet radiation. Owing to the particle size, the sun creams spread more easily, cover better and save money because you use less. The new sun creams are also transparent, unlike traditional sun creams which are white. The use of nanoparticles is so successful that they are now used in more than 300 sun cream products.

Some sun creams contain nanoparticles of titanium oxide. Normal-sized particles of titanium oxide are safe to put on the skin.

It is thought that nanoparticles can pass through the skin and travel around the body more easily than normal-sized particles. It is also thought that nanoparticles might be toxic to some types of cell, such as skin, bone, brain and liver cells.

(a) Explain why nanoparticles pass through the skin and travel around the body more easily than normal-sized particles of titanium oxide.

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(b) Explain why sun creams containing nanoparticles should be tested further.

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(c) Suggest why some companies that make sun creams might not want to do more tests.

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(Total 5 marks)

Keswick School 15

13. Perfumes contain a mixture of chemicals.

The main ingredients of perfumes are a solvent and a mixture of fragrances.

(a) A sample of the solvent used in one perfume contained 0.60 g of carbon, 0.15 g of hydrogen and 0.40 g of oxygen.

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

Calculate the empirical (simplest) formula of the solvent.

You must show all of your working to gain full marks for this question.

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(b) Solvent molecules evaporate easily.

Explain why substances made of simple molecules evaporate easily.

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Keswick School 16

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(c) Most companies claim that their perfumes have been tested on skin. A study was made of the tests they used. The study found that each company used different tests.

The perfumes were tested in the companies’ own laboratories and not by independent scientists.

Some companies did not give any information about the tests that they had used.

(i) Suggest why companies test their perfumes on skin.

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(ii) Did the study show that the tests made by the different companies were valid and reliable?

Explain your answer.

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(Total 9 marks)

Keswick School 17