GCSE & IGCSE chemistry practice

Gas volumes questions and answers

One mole of any gas takes up 24 dm³ (24 000 cm³) at room temperature and pressure (r.t.p.). So volume = moles × 24 dm³, and moles = volume ÷ 24. In an equation, gas volumes react in the same ratio as their moles. Relative atomic masses: H = 1, C = 12, N = 14, O = 16, Na = 23, Mg = 24, Al = 27, S = 32, Cl = 35.5, K = 39, Ca = 40, Fe = 56, Cu = 63.5.

15 questions · Higher tier · Every answer is checked as you type it, with a full worked solution. Updated 10 Nov 2026.

Start the questions

Where gas volumes comes up

GCSE (AQA)	GCSE Chemistry only, Higher only: one mole of any gas occupies 24 dm³ at room temperature and pressure; calculate gas volumes from equations.
Cambridge IGCSE (0620)	Supplement (Extended): use the molar gas volume, 24 dm³ at r.t.p., in calculations involving gases.

The method

Volume (dm³) = moles × 24. Moles = volume ÷ 24.
In cm³: use 24 000.
Gas volumes in an equation are in the same ratio as the moles.
From a mass: moles = mass ÷ Mr first.

Gas volumes questions

Try each one before looking at the hint. If you're stuck, the AI tutor can talk you through it step by step.

Warm-up

Question 1Warm-upHigher

What is the volume of 2 moles of oxygen gas at r.t.p.?

dm³

Question 2Warm-upHigher

How many moles are in 6 dm³ of carbon dioxide at r.t.p.?

mol

Question 9Warm-upHigher

What is the volume of 0.5 mol of nitrogen gas at r.t.p.?

dm³

Question 10Warm-upHigher

How many moles are in 72 dm³ of a gas at r.t.p.?

mol

Exam-style

Question 3Exam-styleHigher

What volume does 0.1 mol of hydrogen occupy at r.t.p., in cm³?

cm³

Question 4Exam-styleHigher

What volume does 8.8 g of carbon dioxide occupy at r.t.p.? ( $M_r$ = 44)

dm³

Question 5Exam-styleHigher

What is the mass of 12 dm³ of oxygen gas, $\text{O}_2$ , at r.t.p.? (O = 16)

Question 6Exam-styleHigher

$2\text{H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O}$ . What volume of oxygen reacts with 50 cm³ of hydrogen (same conditions)?

cm³

Question 11Exam-styleHigher

How many moles are in 480 cm³ of a gas at r.t.p.?

mol

Question 12Exam-styleHigher

What volume does 3.2 g of oxygen gas, $\text{O}_2$ , occupy at r.t.p.? (O = 16)

dm³

Question 13Exam-styleHigher

What is the mass of 36 dm³ of carbon dioxide at r.t.p.? ( $M_r$ = 44)

Challenge

Question 7ChallengeHigher

$\text{CaCO}_3 + 2\text{HCl} \rightarrow \text{CaCl}_2 + \text{H}_2\text{O} + \text{CO}_2$ . What volume of carbon dioxide (at r.t.p.) is made from 5 g of calcium carbonate? ( $M_r$ = 100)

dm³

Question 8ChallengeHigher

$\text{Mg} + 2\text{HCl} \rightarrow \text{MgCl}_2 + \text{H}_2$ . What mass of magnesium gives 360 cm³ of hydrogen at r.t.p.? (Mg = 24)

Question 14ChallengeHigher

$\text{N}_2 + 3\text{H}_2 \rightarrow 2\text{NH}_3$ . What volume of ammonia is made from 60 cm³ of hydrogen (same conditions, all the hydrogen reacts)?

cm³

Question 15ChallengeHigher

$\text{Zn} + 2\text{HCl} \rightarrow \text{ZnCl}_2 + \text{H}_2$ . What volume of hydrogen at r.t.p. is made from 6.5 g of zinc? (Zn = 65)

dm³

Common mistakes

Using 24 for a volume in cm³.
Forgetting to convert the mass to moles first.
Applying 24 dm³ to liquids or solids.

Stuck on one of these?

The TutorAura AI tutor works through it with you step by step, with the reason for each step, then gives you one like it to try. It checks your working too.

Try the AI tutor free

Sources

The questions are our own. The “where it comes up” notes are from each board's published specification, checked on 27 October 2026:

Practise chemistry with your own AI tutor

Questions at your level, help when you're stuck, and a plan for your exams. Free for 3 days, no card needed.

Start free trial