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Leaving Cert Chemistry: Formulas and equations

How often Formulas and equations comes up on the Chemistry papers, every year it was asked, and questions to try.

HL Asked on 7 of the last 10 Higher Level papers, most recently in 2025. most years

OL Asked on 9 of the last 10 Ordinary Level papers, most recently in 2026. banker

June 2027 is the first exam on the new Chemistry course. These come from the 2016–2026 papers, so read them as a guide.

Formulas and equations, Higher Level(8 marks)

Quick ones on Formulas and equations.

(a)Coefficient needed before O2 in: CH4 + ? O2 gives CO2 + 2H2O
  1. 1
  2. 2
  3. 3
(b)Formula of sulfuric acid?
  1. HSO4
  2. H2SO3
  3. H2SO4
(c)Coefficient of O2 in: 2C2H6 + ? O2 gives 4CO2 + 6H2O
  1. 7
  2. 6
  3. 5
Show the answers

(a) 2

(b) H2SO4

(c) 7

Your turn: Higher Level questions on Formulas and equations.

Higher Level

Asked on 7 of the last 10 Higher Level papers, most recently in 2025. most years

Every paper, year by year

YearWhere it came up
2026Not asked
2025Q4(c), Q4(e)
2024Not asked
2023Q4(b)
2022Q10(c)
2021Q4(h), Q10(c)
2019Not asked
2018Q4(i), Q10(c)
2017Q4(h), Q11(a)
2016Q11(a)

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

Ordinary Level

Asked on 9 of the last 10 Ordinary Level papers, most recently in 2026. banker

Every paper, year by year

YearWhere it came up
2026Q4(g), Q4(i)
2025Q4(f), Q4(j)
2024Q4(e), Q10(a)
2023Q4(j)
2022Q4(b), Q4(c), Q4(i), Q4(k)
2021Q4(g), Q11(c)
2019Q4(e), Q4(g)
2018Q4(d), Q4(g)
2017Q4(f)
2016Not asked

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

More Formulas and equations questions

Formulas and equations, 2 marks

Formula of sodium hydroxide?

  1. Na(OH)2
  2. NaO
  3. NaOH
Show the answer

NaOH

Na+ has one positive charge and OH- has one negative charge, so they combine one to one.

Formulas and equations, 2 marks

Formula of magnesium oxide?

  1. MgO2
  2. MgO
  3. Mg2O
Show the answer

MgO

Mg2+ and O2- have equal and opposite charges, so they combine one to one.

Formulas and equations, 2 marks

State symbol for a solid in a chemical equation?

  1. (s)
  2. (l)
  3. (g)
Show the answer

(s)

(s) solid, (l) liquid, (g) gas and (aq) dissolved in water.

Other Chemistry topics

All of Leaving Cert Chemistry