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Leaving Cert Physics & Chemistry: Moles & reacting quantities

How often Moles & reacting quantities comes up on the Physics & Chemistry papers, every year it was asked, and questions to try.

HL Asked on 9 of the last 9 Higher Level papers, most recently in 2025. banker

OL Asked on 9 of the last 9 Ordinary Level papers, most recently in 2025. banker

Moles & reacting quantities, Higher Level(7 marks)

Quick ones on Moles & reacting quantities.

(a)One mole of any substance contains how many particles?
  1. 22.4
  2. 6.0 × 10²³
  3. 12
(b)How many moles are in 8.8 g of CO2? (C = 12, O = 16)
  1. 387 mol
  2. 5 mol
  3. 0.2 mol
(c)Relative molecular mass of H2SO4? (H = 1, S = 32, O = 16)
  1. 98
  2. 50
  3. 49
Show the answers

(a) 6.0 × 10²³

(b) 0.2 mol

(c) 98

Your turn: Higher Level questions on Moles & reacting quantities.

Higher Level

Asked on 9 of the last 9 Higher Level papers, most recently in 2025. banker

Every paper, year by year

YearWhere it came up
2025Q12(b)
2024Q7(a), Q12(b)
2023Q7(j), Q12(a)
2022Q7(e), Q12(a)
2021Q7(e), Q12(a)
2019Q7(d), Q7(i), Q12(a)
2018Q7(j), Q12(a)
2017Q7(j), Q12(a)
2016Q12(c)

Links open the State Examinations Commission’s paper for that year.

More Moles & reacting quantities questions

Moles & reacting quantities, 2 marks

Mass of 0.25 mol of sodium hydroxide, NaOH? (Na = 23, O = 16, H = 1)

  1. 160 g
  2. 0.00625 g
  3. 10 g
Show the answer

10 g

Mr of NaOH = 23 + 16 + 1 = 40. Mass = moles × Mr = 0.25 × 40 = 10 g. Dividing 40 by 0.25 gives 160.

Moles & reacting quantities, 2 marks

Avogadro's law: equal volumes of gases at the same temperature and pressure contain equal…

  1. Numbers of atoms
  2. Numbers of molecules
  3. Masses
Show the answer

Numbers of molecules

The volume of a gas depends on how many molecules it has, not their type. That is why one mole of any gas occupies 22.4 L at s.t.p.

Moles & reacting quantities, 2 marks

How many moles of gas are in 5.6 L at s.t.p.? (molar volume 22.4 L)

  1. 0.25 mol
  2. 4 mol
  3. 125 mol
Show the answer

0.25 mol

Moles = volume ÷ molar volume = 5.6/22.4 = 0.25 mol. 4 is 22.4 ÷ 5.6, the wrong way up; 125 multiplies.

Ordinary Level

Asked on 9 of the last 9 Ordinary Level papers, most recently in 2025. banker

Every paper, year by year

YearWhere it came up
2025Q7(h), Q12(c)
2024Q7(i), Q12(b)
2023Q12(c)
2022Q12(c)
2021Q7(k), Q12(c)
2019Q7(l), Q12(a)
2018Q7(l), Q12(a)
2017Q7(m), Q12(a)
2016Q7(k), Q12(a)

Links open the State Examinations Commission’s paper for that year.

More Moles & reacting quantities questions

Moles & reacting quantities, 2 marks

How many particles are in one mole of a substance?

  1. 6 × 10⁻²³
  2. 22.4
  3. 6 × 10²³
Show the answer

6 × 10²³

This is Avogadro's number. 22.4 is the volume in litres of one mole of gas at s.t.p.

Moles & reacting quantities, 3 marks

Mass of 2 moles of CO2 (C = 12, O = 16)?

  1. 22 g
  2. 88 g
  3. 44 g
Show the answer

88 g

Mr of CO2 = 12 + 16 + 16 = 44, so 1 mole = 44 g. Mass = moles × Mr = 2 × 44 = 88 g.

Moles & reacting quantities, 3 marks

How many moles are in 36 g of water (H = 1, O = 16)?

  1. 2
  2. 0.5
  3. 648
Show the answer

2

Mr of H2O = 2 + 16 = 18. Moles = mass ÷ Mr = 36 ÷ 18 = 2.

Other Physics & Chemistry topics

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