Test for chlorine - AQA GCSE Chemistry Exam Questions

Practise 12 exam-style questions on Test for chlorine for AQA GCSE Chemistry. Write your answer as you would in the exam and get it marked in seconds against the mark scheme, point by point, with an AI tutor on hand if you get stuck.

12 questions
1–6 marks each
Instant marking
No sign-up needed

12 questions, marked as you go

Sample questions with model answers

Here are 4 of the questions in this topic, each with a model answer, an explanation of why it earns the marks and the mark scheme an examiner would use.

Question 1

2 marks

Describe how to test a gas to show that it is chlorine. Give the result of the test.

Model answer

Hold a piece of damp litmus paper in the gas (in a fume cupboard). If the gas is chlorine, the litmus paper is bleached and turns white.

Explanation

The paper must be damp, because chlorine has to dissolve in water to act as a bleach. Blue litmus may turn red for a moment before it is bleached white; the key result is the bleaching.

Mark scheme

1 mark
put damp / moist litmus paper into the gas
damp / moist / wet needed; allow damp universal indicator paper
1 mark
the paper is bleached / turns white
dependent on litmus or indicator paper being used; ignore turns red first

Question 2

2 marks

During the electrolysis of sodium chloride solution, chlorine gas is produced at the positive electrode.

Write a half equation for the formation of chlorine at the positive electrode.

Model answer

2Cl⁻ → Cl₂ + 2e⁻

Explanation

At the positive electrode, negative chloride ions lose electrons (oxidation). Two chloride ions are needed to make one Cl₂ molecule, so two electrons are released, and the charges balance (2− on each side).

Mark scheme

1 mark
Cl⁻ → Cl₂ and electrons
correct species: chloride ions forming chlorine molecules with electrons as a product
1 mark
balanced: 2Cl⁻ → Cl₂ + 2e⁻
allow 2Cl⁻ − 2e⁻ → Cl₂; allow e for e⁻; ignore state symbols

Question 3

3 marks

The diagram shows apparatus for the electrolysis of copper(II) chloride solution. Electrode X is connected to the negative terminal and electrode Y is connected to the positive terminal. A brown solid forms on electrode X and bubbles of gas form on electrode Y.

Name the gas formed at electrode Y and describe a test to identify it.

Diagram of an electrolysis cell. Label X points to the left electrode, connected to the negative terminal; label Y points to the right electrode, connected to the positive terminal.

Model answer

The gas at electrode Y is chlorine. Hold a piece of damp litmus paper near electrode Y: the paper is bleached and turns white.

Explanation

At the positive electrode (anode), chloride ions lose electrons and form chlorine gas; copper forms at the negative electrode. Remember to name the element (chlorine), not the ion (chloride).

Mark scheme

1 mark
chlorine
allow Cl₂; do not accept chloride
1 mark
hold damp litmus paper near / in the gas
damp / moist / wet needed
1 mark
the paper is bleached / turns white
dependent on litmus or indicator paper being used

Question 4

4 marks

Chlorine is made by the electrolysis of sodium chloride solution.

2NaCl(aq) + 2H₂O(l) → 2NaOH(aq) + H₂(g) + Cl₂(g)

Relative atomic masses (Ar): Na = 23, Cl = 35.5
The volume of one mole of any gas at room temperature and pressure is 24 dm³.

Calculate the volume of chlorine produced from 11.7 g of sodium chloride.

Model answer

Mr of NaCl = 23 + 35.5 = 58.5
moles of NaCl = 11.7 ÷ 58.5 = 0.20 mol
2 mol NaCl gives 1 mol Cl₂, so moles of Cl₂ = 0.20 ÷ 2 = 0.10 mol
volume of Cl₂ = 0.10 × 24 = 2.4 dm³

Explanation

Use the 2 : 1 ratio between sodium chloride and chlorine from the balanced equation, then multiply the moles of gas by 24 dm³. The question does not give a unit, so you must state one with your answer.

Mark scheme

1 mark
Mr of NaCl = 58.5
1 mark
moles of NaCl = 11.7 ÷ 58.5 = 0.2(0) mol
allow ecf from an incorrect Mr
1 mark
moles of Cl₂ = 0.20 ÷ 2 = 0.1(0) mol
allow ecf
1 mark
volume = 0.10 × 24 = 2.4 dm³
allow ecf; allow 2400 cm³; unit needed; correct answer with unit and no working scores 4 marks

Ready to try the rest? Every answer you write is marked against the mark scheme, so you can see exactly where the marks are.

AI Tutor Hints first, answers after you try

Hi! Stuck? Ask me for a hint and I’ll help you work it out. Once you’ve checked your answer I can explain exactly where the marks are.