Chemistry

4CH1/2CR — January 2020 (Edexcel IGCSE Chemistry): Past Paper

Exam code:4CH1

7 questions · 70 marks · ≈ 70 min

Complete reconstruction — all 7 questions · 70/70 marks match the official paper

Guided practice

16 marks

(a)(i)

Substances can be classified as elements, mixtures or compounds.

Each box represents an element, a mixture or a compound

Which box represents a mixture?

Choose your answer

(a)(ii)

Which two boxes represent elements?

boxes — official paper figure (qp.pdf p.4)

Choose your answer

1 and 2

2 and 3

1 and 3

3 and 4

2 marks

(a)(iii)

Explain why Box 5 represents a compound.

Your answer

(b)(i)

The Periodic Table contains all the known elements.

How are the elements arranged in the Periodic Table?

Choose your answer

increasing mass number

increasing number of neutrons

increasing number of protons

increasing reactivity

(b)(ii)

Elements in the same group have the same number of

Choose your answer

electrons in the outer shell

electron shells

neutrons

protons

How did you do?/ 6

29 marks

2 marks

(a)

Chromatography is used to analyse mixtures. A student does a chromatography experiment to analyse the composition of green food colouring in sweets. She places four known dyes, A, B, C and D, and the green food colouring on chromatography paper. The diagram shows the student’s apparatus at the start of her experiment

The diagram shows that the student makes two mistakes when setting up her apparatus. State the two changes that the student should make so that her experiment works. 1 2

apparatus — official paper figure (qp.pdf p.8) (same figure as asset_2_a_apparatus_stem)

diagram — official paper figure (qp.pdf p.8) (same figure as asset_2_a_apparatus_stem)

Your answer

3 marks

(b)(i)

Another student does the chromatography experiment correctly. The diagram shows her chromatogram at the end of the experiment. solvent front A B C D Green

Explain what the chromatogram shows about the composition of the green food colouring.

Your answer

3 marks

(b)(ii)

The distance between the start line and the spot for dye C is 6.2 cm. Calculate the Rf value of dye C. Rf value =

Your answer

1 mark

(b)(iii)

Suggest why dye A does not move.

Your answer

How did you do?/ 9

36 marks

(a)

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

What term is used for this reaction?

Choose your answer

neutralisation

precipitation

redox

thermal decomposition

2 marks

(b)

Give two more steps that will produce a pure, dry sample of silver chloride. Step 4 Step 5

Your answer

1 mark

(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.

Your answer

2 marks

(d)

The chemical equation for the reaction between solutions of silver nitrate and potassium chloride is AgNO₃(aq) + KCl(aq) o AgCl(s) + KNO₃(aq) A student adds an excess of potassium chloride solution to 25.0 cm³ 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] mass = g

Your answer

How did you do?/ 6

47 marks

2 marks

(a)

This question is about the metal, lead.

Explain why metals, such as lead, are malleable.

Your answer

1 mark

(b)(i)

A teacher uses this apparatus in a fume cupboard to demonstrate the electrolysis of lead(II) bromide. positive electrode negative electrode lead(II) bromide heat 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.

State why solid lead(II) bromide does not conduct electricity.

Your answer

1 mark

(b)(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. 2Br⁻ o +

Your answer

2 marks

(b)(iii)

Explain why lead metal forms at the negative electrode.

Your answer

1 mark

(b)(iv)

The teacher stops heating the mixture and allows it to solidify. Suggest why the lamp stays alight.

Your answer

How did you do?/ 7

513 marks

2 marks

(a)(i)

This question is about Group 1 metals and their reactions.

When lithium is added to water, bubbles of hydrogen gas are observed.

Give two other observations that could be made. 1 2

Your answer

1 mark

(a)(ii)

Give the test for hydrogen gas.

Your answer

1 mark

(b)(i)

Give one observation that would be different if potassium is used instead of lithium.

Your answer

3 marks

(b)(ii)

The diagram represents an atom of lithium and an atom of potassium. K Li Explain why potassium is more reactive than lithium.

diagram — official paper figure (qp.pdf p.15)

Your answer

3 marks

(c)(i)

The equation for the reaction between lithium and water is 2Li(s) + 2H₂O(l) o 2LiOH(aq) + H₂(g)

A mass of 0.500 g of lithium reacts with an excess of water. Calculate the volume, in cm³, of hydrogen gas produced at rtp. [molar volume of a gas at rtp = 24 000 cm³] Give your answer to three significant figures. volume = cm³

Your answer

3 marks

(c)(ii)

In a reaction between lithium and water, 150 cm³ of lithium hydroxide solution is formed. The lithium hydroxide solution is then completely neutralised by 24.85 cm³ of 0.100 mol/dm³ sulfuric acid. The equation for the neutralisation is 2LiOH(aq) + H₂SO₄(aq) o Li₂SO₄(aq) + 2H₂O(l) Calculate the concentration, in mol/dm³, of the lithium hydroxide solution. concentration = mol/dm³

Your answer

How did you do?/ 13

615 marks

4 marks

(a)

This question is about ethane and ethene.

Ethane can be obtained from crude oil. Describe the industrial process used to separate crude oil into fractions.

Your answer

2 marks

(b)(i)

The equation for the reaction between ethene gas and hydrogen gas is C 2 H4 + H 2 o C 2 H6 The rate of this reaction can be increased by increasing the pressure.

Explain why increasing the pressure increases the rate of this reaction.

Your answer

2 marks

(b)(ii)

The rate of this reaction can also be increased by using a catalyst. Explain how using a catalyst increases the rate of a reaction.

Your answer

1 mark

(b)(iii)

Give one other way that the rate of reaction between ethene gas and hydrogen gas can be increased.

Your answer

3 marks

(b)(iv)

The reaction between ethene and hydrogen is exothermic. Complete the reaction profile diagram, including labels for the activation energy and the enthalpy change, ΔH. C 2 H4 + H 2 Energy

diagram — official paper figure (qp.pdf p.19)

Your answer

3 marks

(c)

The reaction between ethene and hydrogen can be represented using displayed formulae. H H H H C=C + H H –o H C C H H H H H Bond energy in Bond kJ/mol C C 612 C H 412 H H 436 C C 348 Use the bond energies in the table to calculate the enthalpy change, ΔH, in kJ/mol for this reaction. ΔH = kJ/mol

table — official paper figure (qp.pdf p.20)

Your answer

How did you do?/ 15

714 marks

1 mark

(a)(i)

Ethanol, C₂H₅OH, can be produced by the fermentation of glucose, C₆H₁₂O₆

Complete the equation for the fermentation of glucose. C₆H₁₂O₆ o 2C₂H₅OH + 2

Your answer

1 mark

(a)(ii)

State why it is necessary for fermentation to be done in the absence of air.

Your answer

2 marks

(a)(iii)

Explain why the temperature should not be higher than 40 °C.

Your answer

2 marks

(a)(iv)

When 4 mol of glucose is fermented, a mass of 55.2 g of ethanol is produced. Show that the percentage yield of ethanol is 15%. [Mr of C₂H₅OH = 46]

Your answer

2 marks

(b)(i)

Ethanol can also be produced by the reaction between ethene and steam. The equation for the reaction is C₂H₄(g) + H₂O(g) U C₂H₅OH(g)

This reaction is in dynamic equilibrium. Give two features of a reaction in dynamic equilibrium. 1 2

Your answer

2 marks

(b)(ii)

When the equilibrium mixture is heated, the yield of ethanol decreases. Explain whether the forward reaction is exothermic or endothermic.

Your answer

2 marks

(c)(i)

Carboxylic acids react with alcohols to form esters

Carboxylic acid A and alcohol B react to produce this ester. Give the displayed formula of carboxylic acid A and of alcohol B. Carboxylic acid A Alcohol B

displayed formula of an ester — official paper figure (qp.pdf p.23)

Your answer

2 marks

(c)(ii)

Indicators can be used to test for carboxylic acids. Describe a different chemical test for a carboxylic acid.

Your answer

How did you do?/ 14

16 marks

(a)(i)

Substances can be classified as elements, mixtures or compounds.

Each box represents an element, a mixture or a compound

Which box represents a mixture?

Choose your answer

(a)(ii)

Which two boxes represent elements?

boxes — official paper figure (qp.pdf p.4)

Choose your answer

1 and 2

2 and 3

1 and 3

3 and 4

2 marks

(a)(iii)

Explain why Box 5 represents a compound.

Your answer

(b)(i)

The Periodic Table contains all the known elements.

How are the elements arranged in the Periodic Table?

Choose your answer

increasing mass number

increasing number of neutrons

increasing number of protons

increasing reactivity

(b)(ii)

Elements in the same group have the same number of

Choose your answer

electrons in the outer shell

electron shells

neutrons

protons

How did you do?/ 6