Name: _______________________________________________

Summer Worksheet
Chemistry IGCSE

Date:

Time:

Total marks available:

Total marks achieved: ______

Mrs. Sara Rawass

Questions
Q1.

Halon 1301 is a compound used in some fire extinguishers.

Halon 1301 has the percentage composition by mass of

(a) Show, by calculation, that the empirical formula of this compound is CBrF3
(2)

(b) The diagram shows the displayed formula of a molecule of Halon 1301.

Draw a dot-and-cross diagram to show all the outer electrons in this molecule.
(2)

(c) The boiling point of Halon 1301 is −58 °C.

Explain why Halon 1301 has a low boiling point.
(2)
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(Total for question = 6 marks)

Q2.
This question is about carbon and its compounds.

(a) (i) Draw a dot-and-cross diagram to show the outer shell electrons in a molecule of carbon dioxide,
CO2
(2)

(ii) The atoms in carbon dioxide are held together by covalent bonds.
Describe the forces of attraction in a covalent bond.
(2)
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(b) The diagram shows three different structures of carbon.

(i) Explain why graphite conducts electricity.

(2)
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 (ii) Explain why diamond has a much higher melting point than C60 fullerene.
Refer to structure and bonding in your answer.
(5)
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(Total for question = 11 marks)

Q3.

This question is about copper and copper compounds.

(a) A sample of copper contains two isotopes.

 Cu-63 with relative abundance 69.5%

 Cu-65 with relative abundance 30.5%
(i) State what is meant by the term isotopes.
(2)
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(ii) Calculate the relative atomic mass (Ar) of this sample of copper.
 Give your answer to three significant figures.
(3)

Ar of copper = ...........................................................

(b) When copper(II) carbonate is heated, copper(II) oxide and carbon dioxide are formed.
(i) What is the name of this type of reaction?
(1)
A decomposition
B neutralisation
C oxidation
D reduction

(ii) Which colour change occurs during this reaction?

(1)
A blue to black
B blue to white
C green to black
D green to orange

(c) A student uses this apparatus to find the value of x in the formula CuSO 4.xH2O

This is the student's method.

 find the mass of an empty boiling tube

 add hydrated copper(II) sulfate to the tube and record the new mass
 heat the hydrated copper(II) sulfate until it changes colour
 allow the tube to cool and record the mass again
The table shows the student's results.
 (i) Calculate the mass of CuSO4 formed.
(1)
mass of CuSO4 = ........................................................... g
(ii) Calculate the mass of water formed.
(1)
mass of water = ........................................................... g
(iii) Show that the value of x is approximately 4
[Mr of CuSO4 = 159.5 Mr of H2O = 18]
(3)

(iv) The actual value of x is 5

Give a reason why the calculated value of x is lower than the actual value.
(1)
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(Total for question = 13 marks)

Q4.

(a) Chlorine, bromine and iodine are elements in the Periodic Table.
Explain how the position of these elements in the Periodic Table depends on their
electronic configurations.
(2)
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(b) Chlorine reacts with methane to form CH 3Cl and HCl
(i) State the condition necessary for this reaction.
(1)
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(ii) Give the equation for this reaction.
(1)
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(iii) The bonds in a molecule of CH3Cl are covalent.
Explain, in terms of electrostatic attractions, what is meant by a covalent bond.
(2)
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(iv) Draw a dot-and-cross diagram for a molecule of CH 3Cl
Show only the outer electrons of the atoms.
(2)

(v) CH3Cl has a simple molecular structure.

Explain why CH3Cl has a low boiling point.
(2)
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(c) Graphite is another substance that contains covalent bonds.

 The diagram shows the structure of graphite.

Most covalent substances do not conduct electricity.

Explain why graphite is able to conduct electricity.
(2)
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(Total for question = 12 marks)

Q5.

This question is about gases.

(a) The table gives information about some gases.

Complete the table by choosing a gas from the box that matches the information.

You may use each gas once, more than once, or not at all.
(4)
(b) A teacher uses this apparatus to determine the percentage of oxygen in a sample of air.

This is the teacher's method.

 record the total volume of air in the apparatus

 heat the copper powder
 use the syringes to pass air over the heated copper powder several times
 allow the remaining gas to cool and record its volume
The copper powder turns black.

(i) State why the copper powder turns black.

(1)
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(ii) Give a reason why the remaining gas is allowed to cool before its volume is recorded.
(1)
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(iii) At the start of the experiment, the total volume of air in the apparatus is 138 cm 3.
At the end of the experiment, the volume of gas remaining is 108 cm 3.
Calculate the percentage of oxygen in the sample of air.
Assume that all the oxygen has reacted.
(2)
 percentage of oxygen = ........................................................... %

(Total for question = 8 marks)

Q6.

This question is about Group 7, the halogens.

(a) Which halogen has the palest colour?

(1)
A astatine
B bromine
C fluorine
D iodine

(b) Which halogen is a solid at room temperature?

(1)
A astatine
B bromine
C chlorine
D fluorine

(c) The table shows the electronic configurations of a fluorine atom and a chlorine atom.

Explain the relative reactivities of fluorine and chlorine using the information in the table.
(4)
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(d) Lithium reacts with chlorine to form lithium chloride.

(i) Write a chemical equation for the reaction of lithium with chlorine.
(1)
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(ii) Describe tests to show that the product of the reaction is lithium chloride.
(5)
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(Total for question = 12 marks)

Q7.

A student uses this method to investigate the reaction of dilute hydrochloric acid with zinc.

 pour some dilute hydrochloric acid into a glass beaker

 record the initial temperature of the acid
 add a piece of zinc and stir the mixture
 record the temperature of the mixture after one minute
(a) Write a word equation for the reaction of dilute hydrochloric acid with zinc.
(1)
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(b) The diagram shows the thermometer readings for this reaction.
 Complete the table, giving all values to the nearest 0.1°C.
(3)

(c) Another student repeats the method using five different metals to compare their
reactivity.
(i) This student uses a polystyrene cup instead of a glass beaker.
Explain why a polystyrene cup is better than a glass beaker in this investigation.
(2)
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(ii) Give three factors that the student should keep constant in this investigation.
(3)
1 ..........................................................................................................................................

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

3 ..........................................................................................................................................

(d) The table shows some of the student's results.

 (i) State why there is no temperature change for copper.
(1)
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(ii) Predict the temperature change for iron.
(1)

temperature change = ........................................................... °C

(iii) Deduce the order of reactivity of the five metals.
(1)
most reactive
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least reactive

(Total for question = 12 marks)

Q8.

Thallium, Tl, is an element in Group 3 and Period 6 of the Periodic Table.

The atomic number of thallium is 81

(a) How many electrons are there in the outer shell of an atom of thallium?
(1)
A 3

B 6

C 13

D 81

(b) A thallium ion has a charge of 3+

How many electrons are there in this thallium ion?
(1)
A 3

B 78

C 81

D 84

(c) A sample of thallium contains two isotopes.

The table shows the mass number and percentage abundance of each isotope in the
sample.

(i) Give the number of protons and the number of neutrons in one atom of the thallium-
205 isotope.
(2)
number of
protons ...........................................................................................................................

number of
neutrons .........................................................................................................................

(ii) Calculate the relative atomic mass of this sample of thallium.

Give your answer to one decimal place.
(3)
 relative atomic mass = ...........................................................

(Total for question = 7 marks)

Q9.

The diagram shows the positions of some elements in the Periodic Table.

(a) Use symbols from this table to answer these questions.

Each symbol may be used once, more than once or not at all.
(i) Give the symbol of a metal.
(1)
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(ii) Give the symbol of a noble gas.
(1)
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(iii) Give the symbol of a liquid at room temperature.
(1)
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(iv) Give the symbols of the two elements in Period 3
(1)
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(b) Deduce the electronic configuration of Na

(1)
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(Total for question = 5 marks)

Q10.
A student is provided with a bottle containing a colourless solution X.

Solution X is thought to be dilute sulfuric acid of concentration 0.10 mol/dm 3.

The student does some experiments on samples of solution X to try to show that it is dilute
sulfuric acid.

The student adds a few drops of litmus to a sample of solution X.

The litmus turns red.

(a) The student knows that the products of the electrolysis of dilute sulfuric acid are
hydrogen and oxygen.
She carries out the electrolysis using this apparatus.

(i) Suggest why the student does not use zinc electrodes in her experiment.
(1)
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(ii) State what is observed at both the anode and the cathode during the electrolysis.
(1)
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(iii) Which of these tests shows that the gas formed at the cathode is hydrogen?
(1)
A a glowing splint relights
B a burning splint gives a squeaky pop
C a burning splint goes out
D limewater turns cloudy
(b) Describe a test to show that solution X contains sulfate ions.
(2)
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(c) The student then does a titration to see if the concentration of the dilute sulfuric acid is
0.10 mol/dm3.
She measures 25.0 cm3 of potassium hydroxide solution into a conical flask, and then
adds a few drops of indicator solution.
(i) Name the piece of apparatus the student should use to measure 25.0 cm 3 of the
potassium hydroxide solution.
(1)
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(ii) The concentration of potassium hydroxide in the solution is 0.125 mol/dm 3.
Calculate the amount, in mol, of KOH in 25.0 cm 3 of this solution.
(2)

amount = ........................................................... mol

(iii) The equation for the reaction in the titration is
H2SO4 + 2KOH → K2SO4 + 2H2O
Calculate the volume, in cm3, of 0.10 mol/dm3 sulfuric acid needed to neutralise 25.0
cm3 of
the potassium hydroxide solution.
(3)

volume of sulfuric acid = ........................................................... cm 3

(Total for question = 11 marks)

Q11.

Food colourings contain one or more food dyes.

A student has samples of three pure food dyes, A, B and C.

She uses chromatography to investigate the composition of a food colouring, U.

She uses a pencil to draw a line and label A, B, C and U on chromatography paper.

She uses water as the solvent.

The diagram shows the appearance of the paper before and after the experiment.

(a) (i) Describe the method that the student could have used to obtain her results.
(3)
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 (ii) Describe the composition of food colouring U.
(2)
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(iii) Suggest why food dye A does not move in the experiment.
(1)
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(b) Dyes can be identified by their Rf values.

Calculate the Rf value of food dye B.

(2)

Rf value = ...........................................................

(c) The student repeats the experiment using solvent X instead of water.
(i) Solvent X produces a flammable vapour.
Give a safety precaution that the student should take when using solvent X.
(1)
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(ii) Suggest why the Rf value of food dye C might be greater when solvent X is used
instead of water.
(1)
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(Total for question = 10 marks)

Q12.

The table gives some information about three substances, X, Y and Z.

(a) Complete the table by giving the missing information.

(4)
(b) Explain why substance X has a low melting point.
(2)
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(Total for question = 6 marks)

Q13.

Sodium hydroxide dissolves in water, forming a strongly alkaline solution.

Ammonia dissolves in water, forming a slightly less alkaline solution.

(a) (i) Identify the ion that makes the sodium hydroxide solution alkaline.
(1)
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(ii) What is a possible pH of ammonia solution?
(1)
A 3
B 6
C 11
D 14

(b) When ammonia solution reacts with sulfuric acid, a neutralisation reaction occurs and
ammonium sulfate forms.
(i) How does the sulfuric acid act in this reaction?
(1)
A as a neutron donor
B as a neutron acceptor
C as a proton donor
D as a proton acceptor

(ii) The diagram shows a beaker containing some ammonia solution and a few drops of
phenolphthalein indicator.

Dilute sulfuric acid is added to the beaker until it is in excess.

What are the colours of the phenolphthalein indicator before and after adding excess
sulfuric acid?
(1)

(c) Ammonium sulfate is used by gardeners as a fertiliser because it contains nitrogen.

(i) Explain why the chemical formula of ammonium sulfate is (NH 4)2SO4
Refer to the charges on the ions in your answer.
(2)
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(ii) Calculate the relative formula mass of ammonium sulfate, (NH 4)2SO4
 (1)

relative formula mass = ...........................................................

(iii) Calculate the mass, in grams, of nitrogen in 1.0 kg of ammonium sulfate.

(3)

mass = ........................................................... g

(Total for question = 10 marks)

Q14.

A student uses this method to do a titration.

 use a measuring cylinder to obtain 25 cm 3 of sodium hydroxide solution

 transfer the solution to a conical flask
 add a few drops of universal indicator to the flask
 fill a burette with dilute sulfuric acid and record the initial burette reading
 add the acid to the flask, swirling the flask continuously
 add the acid slowly near the end-point
 record the final burette reading at the end-point
The student repeats the titration until at least two concordant results are obtained.

(a) State what is meant by concordant results.

(1)
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(b) Explain two improvements to the student's method so that more accurate results are
obtained.
 (4)
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(c) The student makes the improvements and repeats the titration.
The sulfuric acid has a concentration of 0.600 mol/dm 3.
The sodium hydroxide solution has a concentration of 1.50 mol/dm 3.
This is the equation for the reaction.
2NaOH + H2SO4 → Na2SO4 + 2H2O
Calculate the volume, in cm3, of sulfuric acid that the student needs to completely react
with 25.0 cm3 of the sodium hydroxide solution.
(3)

volume of sulfuric acid = ........................................................... cm 3

(d) The student plans to obtain pure dry crystals of hydrated sodium sulfate.
They add the calculated volume of sulfuric acid to 25.0 cm 3 of the sodium hydroxide
solution to form sodium sulfate solution.
Describe what the student should do to obtain pure dry crystals of hydrated sodium
sulfate from the solution.
(4)
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(Total for question = 12 marks)

Q15.

This question is about the three halogens, bromine, chlorine and iodine.

(a) Give the number of protons and the number of neutrons in an atom of iodine-127
(2)
number of protons
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number of neutrons
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(b) A sample of bromine contains two isotopes.

 Br-79 with relative abundance 52.8%

 Br-81 with relative abundance 47.2%
Calculate the relative atomic mass (Ar) of this sample of bromine.
Give your answer to three significant figures.
(3)

Ar ...........................................................

(c) Aluminium reacts with chlorine to form aluminium chloride.

This is the equation for the reaction.

Calculate the minimum mass of chlorine needed to form 26.7 g of aluminium chloride.
 [for Cl2 , Mr = 71 for AlCl3 , Mr = 133.5]
(3)

minimum mass of chlorine = ........................................................... g

(d) A student mixes the following pairs of solutions.

Pair 1 bromine solution and potassium chloride solution
Pair 2 bromine solution and potassium iodide solution
Explain how the student can use the results of these experiments to show the order of
reactivity of the three halogens, bromine, chlorine and iodine.
Include observations in your answer.
(6)
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(Total for question = 14 marks)

Q16.

Answer the questions with a cross in the boxes you think are correct . If you
change your mind about an answer, put a line through the box and then mark
your new answer with a cross .

The diagram shows the particles in an atom of an element.

(a) Name the particles labelled P, Q and R.

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

Q .........................................................................................................................................

R .........................................................................................................................................

(b) Name the part of the atom labelled S.

(1)
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(c) (i) What is the atomic number of this atom?

(1)
A 5
B 7
C 12
D 17

(ii) What is the mass number of this atom?

(1)
A 5
B 7
C 12
D 17
 (iii) Identify this element.
(1)
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(Total for question = 7 marks)

Q17.

This question is about the rusting of iron.

(a) Water is needed for iron to rust.

(i) Name one other substance needed for iron to rust.
(1)
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(ii) Give the chemical name for rust.
(1)
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(b) The diagram shows two methods used to prevent iron from rusting.

Method A will only work if the plastic coating is not damaged.

Method B will work even when the zinc coating is damaged.
(i) Explain how method A prevents iron from rusting.
(2)
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(ii) Give the name of method B.
(1)
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(iii) Explain how method B prevents iron from rusting even when the zinc coating is
damaged.
(2)
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(Total for question = 7 marks)

Q18.

This question is about the reduction of metal oxides.

(a) Solid oxides of copper can be reduced by reacting them with methane gas.
Complete the equation for the reaction between copper(II) oxide and methane.
Include state symbols.
(2)
............CuO(............) + ............CH4(............)
→ ............Cu(............) + ............CO2(............) + ............H2O(............)

(b) A teacher uses this apparatus to demonstrate the reaction between a different oxide of
copper and methane.

(i) The teacher heats the oxide of copper until the reaction is complete.
The table shows the teacher's results.

Use the teacher's results to show that the empirical formula of this oxide of copper is
Cu2O
(4)
 (ii) The teacher wears safety glasses and a lab coat during the demonstration.
Give one other safety precaution that she should take.
(1)
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(c) Iron forms when iron(III) oxide is heated with carbon.

The equation for the reaction is
Fe2O3 + 3C → 2Fe + 3CO
(i) State how the equation shows that iron(III) oxide is reduced.
(1)
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(ii) State why carbon monoxide should not be released into the atmosphere.
(1)
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(iii) Calculate the maximum mass, in tonnes, of iron that can be produced when 30.0
tonnes of iron(III) oxide are reacted with an excess of carbon.
[1 tonne = 1.0 × 106 g]
(4)

mass = ........................................................... tonnes

(iv) A mixture of 25 000 mol of iron(III) oxide and 840 000 g of carbon is heated.
Use this equation to show that the iron(III) oxide is in excess.
Fe2O3 + 3C → 2Fe + 3CO
(2)
 (Total for question = 15 marks)

Q19.

This question is about the reactions of iron.

(a) Iron rusts when exposed to water and oxygen.

(i) Give the chemical name of the compound that forms when iron rusts.
(1)
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(ii) What type of reaction occurs when iron rusts?
(1)
A combustion
B decomposition
C neutralisation
D oxidation

(iii) Galvanising is a method used to prevent iron from rusting.

Give the name of the metal used to galvanise iron.
(1)
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(b) When iron reacts with dilute sulfuric acid, the products are iron(II) sulfate and hydrogen.
(i) Give a chemical equation for the reaction between iron and sulfuric acid.
(1)
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(ii) Give a test for hydrogen.
(1)
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(c) An excess of iron is added to copper(II) sulfate solution.

(i) Name the type of reaction that occurs.
(1)
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(ii) State the appearance of the solid that forms in the reaction.
(1)
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(d) Give the reason why no reaction occurs when iron is added to magnesium sulfate
solution.
 (1)
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(Total for question = 8 marks)

Q20.

This question is about the metal, lead.

(a) Explain why metals, such as lead, are malleable.

(2)
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(b) A teacher uses this apparatus in a fume cupboard to demonstrate the electrolysis of
lead(II) bromide.

The lead(II) bromide is heated until it melts.

When the lead(II) bromide melts, the lamp lights.
One of the products of this electrolysis is lead.
(i) State why solid lead(II) bromide does not conduct electricity.
(1)
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(ii) Bromine is formed by the oxidation of bromide ions at the positive electrode.
Complete the ionic half-equation for the oxidation of bromide ions.
(1)
2Br– → ............................................... + ...............................................
(iii) Explain why lead metal forms at the negative electrode.
(2)
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(iv) The teacher stops heating the mixture and allows it to solidify.
Suggest why the lamp stays alight.
(1)
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(Total for question = 7 marks)

Q21.

This question is about the insoluble salt, lead(II) bromide.

Lead(II) bromide can be made by a precipitation reaction.

This is the equation for the reaction.

(a) Describe how solutions of lead nitrate and potassium bromide can be used to make a
pure, dry sample of lead(II) bromide.
(4)
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(b) A solution containing 0.150 mol of lead(II) nitrate is reacted with an excess of potassium
bromide solution.
A mass of 49.6 g of pure, dry lead(II) bromide is produced.
Show, by calculation, that the percentage yield of lead(II) bromide is 90.1%.
[for PbBr2, Mr = 367]
(2)

(c) A student investigates the change in electrical conductivity as dilute lead(II) nitrate
solution is added to dilute potassium bromide solution.
This is the student's method.
Step 1 add 50 cm3 of potassium bromide solution to a beaker
Step 2 measure the electrical conductivity of the solution
Step 3 add 10 cm3 of lead(II) nitrate solution to the beaker
Step 4 stir the mixture
Step 5 measure the electrical conductivity of the mixture
Repeat steps 3, 4 and 5 until a total of 50 cm 3 of lead(II) nitrate solution has been added.
The table shows the student's results.

(i) Plot the student's results on the grid.

(1)
(ii) Draw a line of best fit, ignoring the anomalous result.
(1)

(iii) Explain the shape of the graph.

(2)
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(iv) Suggest a mistake the student could have made to cause the anomalous result.
(1)
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(v) Further 10 cm3 volumes of lead(II) nitrate are added to the beaker so the lead(II) nitrate
is in excess.
Predict what will happen to the conductivity of the mixture when the lead(II) nitrate is in
excess.
(1)
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(d) The diagram shows the electrolysis of molten lead(II) bromide, PbBr 2
This is the ionic half-equation for the formation of bromine at electrode A.

Give a reason why this half-equation shows oxidation.

(1)
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(Total for question = 13 marks)

Q22.

The formation of ions and covalent bonds involves electrons.

The table gives the electronic configurations of atoms of hydrogen, lithium and chlorine.

(a) Describe the different roles of electrons in the formation of

 ions in lithium chloride

 covalent bonds in hydrogen chloride
(3)
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(b) Explain why lithium chloride has a higher melting point than hydrogen chloride.
Refer to structure and bonding in your answer.
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(Total for question = 8 marks)

Q23.

(a) A scientist finds an unlabelled bottle on a shelf.

She thinks the bottle contains a solution of ammonium sulfate, (NH 4)2SO4
Describe tests the scientist could do to show that the solution is ammonium sulfate.
(6)
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(b) Ammonium sulfate is often used as a fertiliser.

It is prepared by reacting ammonia (NH 3) with sulfuric acid (H2SO4).
(i) Name the type of reaction that occurs between ammonia and sulfuric acid.
(1)
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(ii) Write a chemical equation for the reaction of ammonia with sulfuric acid.
(1)
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(iii) Draw a dot-and-cross diagram to show the bonding in a molecule of ammonia.
Show outer electrons only.
(2)
 (Total for question = 10 marks)

Q24.

The gas burned in a Bunsen burner is methane.

The equation for the complete combustion of methane is

(a) Calculate the mass of oxygen required to react with 32 g of methane.

[Mr of methane = 16]
(2)

mass of oxygen = ........................................................... g

(b) The diagram shows methane burning in air. It also shows how the two gases formed are
collected and tested.

(i) Explain why water collects in the U-tube.

(2)
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(ii) Describe how anhydrous copper(II) sulfate is used to test for water.
(2)
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(iii) Explain the change in appearance of the limewater.
(3)
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(Total for question = 9 marks)

Q25.

(a) The diagram shows the particles in four substances, A, B, C and D.

(i) Which substance contains single atoms of one element?

(1)
A
B
C
D

(ii) Which substance is a compound?

(1)
A
B
C
D

(iii) Which substance could have the formula H 2?

(1)
A
B
C
D
(b) The diagram shows the particles in substance E.

Give two reasons why substance E is a mixture.

(2)
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(Total for question = 5 marks)

Q26.

Solutions of silver nitrate and potassium chloride react together to make the insoluble salt,
silver chloride.

A student uses this method to prepare a sample of silver chloride.

Step 1 add 25 cm3 of silver nitrate solution to a conical flask
Step 2 add potassium chloride solution to the flask
Step 3 filter off the silver chloride
(a) What term is used for this reaction?
(1)
A neutralisation
B precipitation
C redox
D thermal decomposition

(b) Give two more steps that will produce a pure, dry sample of silver chloride.
(2)
Step 4 ...................................................................................................................................

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Step 5 ..................................................................................................................................
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(c) Acidified silver nitrate solution is used to test for chloride ions.
Give a reason why hydrochloric acid is not used to acidify silver nitrate solution.
(1)
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(d) The chemical equation for the reaction between solutions of silver nitrate and potassium
chloride is

AgNO3(aq) + KCl(aq) → AgCl(s) + KNO3(aq)

A student adds an excess of potassium chloride solution to 25.0 cm 3 of 0.100 mol/dm3
silver nitrate solution.
Calculate the maximum mass of silver chloride, in grams, that can be produced.
[Mr of AgCl = 143.5]
(2)

mass = ........................................................... g

(Total for question = 6 marks)

Q27.

(a) Sodium chloride is an ionic compound.

Explain why sodium chloride conducts electricity when it is molten or in solution, but not
when it is solid.
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(b) A solution of sodium chloride can be electrolysed using this apparatus.

(i) If the solution is dilute, a significant amount of oxygen collects at P.

Complete the ionic half-equation for this reaction.
(1)
+ –
................H2O → ................H + ................O2 + ................e
(ii) If the solution is concentrated, chlorine is the main product that collects at P.
This is the ionic half-equation for the reaction.
2Cl– → Cl2 + 2e–
State why this is an oxidation reaction.
(1)
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(c) The gas that collects at Q is hydrogen.

(i) Give a test for hydrogen.
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(ii) Explain how hydrogen gas forms at the negative electrode.
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(d) Hydrogen reacts with oxygen to form water.

The equation shows the covalent bonds in the molecules.

The table gives the bond energies.

(i) Use the equation and the values in the table to calculate the enthalpy change, ΔH, for
the reaction.
Include a sign in your answer.
(3)

ΔH = ........................................................... kJ
(ii) Complete the diagram to show the energy levels of the reactants and products, and
the enthalpy change, ΔH.
(3)

(Total for question = 14 marks)

Q28.

A student uses this apparatus to investigate the dyes in a food colouring A.

(a) Explain two mistakes that the student makes when setting up the apparatus.
(4)
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(b) The student repeats the experiment, but with no mistakes.

The table shows the Rf values for the two dyes in food colouring A.

(i) Complete the chromatogram for food colouring A by adding and labelling the dyes.
(2)
 (ii) Give a reason why the blue dye has a larger R f value than the yellow dye.
(1)
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(Total for question = 7 marks)