A mole is a counting unit: one mole holds 6.02 times ten to the twenty-three particles, just as a dozen holds twelve.

Must gas volume use 24.0 dm3?

Room temperature and pressure use 24.0 dm3 while standard conditions use 22.4 dm3, and the question decides.

S4 Chemistry: The Mole (Paper 1)

2026-11-01

Tutor Prep Guide · Secondary Chemistry

This paper builds the mole basics: converting between mass, moles, particles and gas volume.

Direct answer　Turn mass into moles first, then use the Avogadro constant or molar volume for particles or volume.

01　Paper details (check answers afterwards)

Item	Detail
Questions	10
Suggested time	25
Difficulty mix	Foundation 4 · Intermediate 3 · Challenge 2 · Error redo 1
Chapter	Chapter: S4 Chemistry: The Mole, Concentration and Percentage Yield
Level	Four basic, three advanced, two challenge and one error-repair item

02　Questions (10 items)

FoundationHow many moles are there in 8.0 g of oxygen gas, O2, with O = 16?
FoundationWhat is the mass of 0.50 mol of carbon dioxide, CO2, with C = 12 and O = 16?
FoundationHow many water molecules are in 3.0 mol of water, with the Avogadro constant 6.02 times ten to the twenty-three?
FoundationWhat is the molar mass of calcium carbonate, CaCO3, with Ca = 40, C = 12 and O = 16?
IntermediateHow many moles are in 11.2 dm3 of gas at room temperature, taking 24.0 dm3 per mole?
IntermediateHow many moles are in 4.8 dm3 of gas at room temperature?
IntermediateA 0.20 mol sample has a mass of 8.0 g. Find its molar mass.
Challenge12.0 g of magnesium burns completely. How many moles and what mass of oxygen are needed with Mg = 24 and O = 16?
ChallengeHeating 5.0 g of calcium carbonate should give how many moles of carbon dioxide and what volume at room temperature?
Error redoError repair: a student writes that one mole of any substance occupies 22.4 dm3. Correct it.

03　Answers and one-line notes

#	Answer	One-line note
1	0.25 mol	The molar mass is 32 g per mole, so 8.0 divided by 32 gives 0.25 mol.
2	22 g	The molar mass is 44 g per mole, so 0.50 times 44 is 22 g.
3	1.81 times ten to the twenty-four	3.0 times 6.02 times ten to the twenty-three is 1.806 times ten to the twenty-four, or 1.81 times ten to the twenty-four.
4	100 g/mol	40 plus 12 plus three sixteens gives 100 g per mole.
5	0.467 mol	11.2 divided by 24.0 is 0.4667, which rounds to 0.467 mol.
6	0.20 mol	4.8 divided by 24.0 is exactly 0.20 mol.
7	40 g/mol	Molar mass is mass divided by moles, so 8.0 divided by 0.20 is 40 g per mole.
8	0.25 mol, that is 8.0 g	The magnesium is 0.50 mol and the equation uses two magnesiums per oxygen, so 0.25 mol or 8.0 g of oxygen is needed.
9	0.05 mol, that is 1.2 dm3	5.0 divided by 100 gives 0.05 mol and the ratio to carbon dioxide is one to one, so the volume is 1.2 dm3.
10	molar volume applies to gases only and is 24.0 dm3 at room temperature	Molar volume applies to gases only, and at room temperature it is 24.0 dm3; solids and liquids depend on density.

04　What to do after marking

After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
Repeat the same item two days later; move to the next paper only when both attempts are correct.
Parents only need the answer and note columns; there is no need to explain every item.

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Questions and answers are written originally by the TutorZone team and are not taken from any school, publisher or examination authority paper. Every value is checked by computer.