Test for hydrogen - AQA GCSE Chemistry Exam Questions

Practise 11 exam-style questions on Test for hydrogen 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.

11 questions
1–5 marks each
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11 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

A student writes this description of the test for hydrogen:

"Put a glowing splint into the test tube of gas. If the gas is hydrogen, the splint relights."

Give two corrections to the student's description.

Model answer

The splint should be a burning (lighted) splint, held at the open end of the test tube, not a glowing splint. If the gas is hydrogen it burns with a squeaky pop; a glowing splint relighting is the test for oxygen.

Explanation

Students often mix up the hydrogen and oxygen tests. Hydrogen needs a flame to ignite it, so a burning splint is used and the result is a pop; oxygen is tested with a glowing splint, which relights.

Mark scheme

1 mark
use a burning splint (not a glowing splint)
allow lighted / lit splint; allow held at the open end / mouth of the tube
1 mark
the result is a (squeaky) pop (not relighting)
allow burns with a pop; ignore references to the oxygen test unless used instead of a correct result

Question 2

2 marks

A student adds a piece of copper to dilute hydrochloric acid in a test tube. The student holds a burning splint at the open end of the tube. There is no pop.

Explain this result.

Model answer

Copper is less reactive than hydrogen, so it cannot displace hydrogen from the acid. Copper does not react with dilute hydrochloric acid, so no hydrogen is made and there is nothing to give a pop.

Explanation

Only metals above hydrogen in the reactivity series react with dilute acids to give hydrogen. With copper there is no reaction, so the hydrogen test is negative.

Mark scheme

1 mark
copper is less reactive than hydrogen
allow copper is below hydrogen in the reactivity series
1 mark
so copper does not react with the acid / no hydrogen is produced

Question 3

3 marks

The diagram shows apparatus used for the electrolysis of sodium chloride solution. Tube A collects the gas from the negative electrode (cathode). Tube B collects the gas from the positive electrode (anode).

Identify the gas collected in tube A and describe a test to show that it is this gas.

Diagram of an electrolysis cell. Label A points to the upside-down test tube over the left electrode; label B points to the upside-down test tube over the right electrode; "sodium chloride solution" labels the liquid in the container.

Model answer

The gas in tube A is hydrogen. Hold a burning splint at the open end of the tube; the hydrogen burns with a squeaky pop.

Explanation

In sodium chloride solution, hydrogen is less reactive than sodium, so hydrogen ions from the water are discharged at the cathode as hydrogen gas. The test result must be linked to the correct splint: a burning splint gives a pop with hydrogen.

Mark scheme

1 mark
hydrogen
allow H₂
1 mark
hold a burning splint at the open end of the tube
allow lighted / lit splint; do not accept glowing splint
1 mark
(squeaky) pop
dependent on a burning splint being used

Question 4

4 marks

A student reacts 0.12 g of magnesium with excess dilute hydrochloric acid.

Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g)

Relative atomic mass (Ar): Mg = 24
The volume of one mole of any gas at room temperature and pressure is 24 dm³.

Calculate the maximum volume of hydrogen produced, in cm³.

Model answer

moles of Mg = mass ÷ Ar = 0.12 ÷ 24 = 0.0050 mol
From the equation, 1 mol Mg gives 1 mol H₂, so moles of H₂ = 0.0050 mol
volume of H₂ = 0.0050 × 24 = 0.12 dm³
0.12 dm³ × 1000 = 120 cm³

Explanation

Convert the mass of the limiting reactant to moles, use the equation to find moles of hydrogen, then multiply by 24 dm³ to get the volume. Remember 1 dm³ = 1000 cm³, a common place to lose the final mark.

Mark scheme

1 mark
moles of Mg = 0.12 ÷ 24 = 0.005(0) mol
1 mark
moles of H₂ = 0.005(0) mol
allow ecf; 1:1 ratio from the equation
1 mark
volume = 0.0050 × 24 = 0.12 dm³
allow ecf
1 mark
= 120 (cm³)
allow ecf for correct conversion of an incorrect volume in dm³ (× 1000); correct answer with no working scores 4 marks

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