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Leaving Cert Chemistry: Acids and bases

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

HL Asked on 10 of the last 10 Higher Level papers, most recently in 2026. banker

OL Asked on 8 of the last 10 Ordinary Level papers, most recently in 2025. most years

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

Acids and bases, Higher Level(7 marks)

Quick ones on Acids and bases.

(a)Bronsted-Lowry definition of an acid?
  1. A proton acceptor
  2. A proton donor
  3. An electron pair donor
(b)Conjugate base of sulfuric acid, H2SO4?
  1. H3SO4+
  2. SO4 2-
  3. HSO4-
(c)Bronsted-Lowry definition of a base?
  1. A proton acceptor
  2. An electron pair acceptor
  3. A proton donor
Show the answers

(a) A proton donor

(b) HSO4-

(c) A proton acceptor

Your turn: Higher Level questions on Acids and bases.

Higher Level

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

Every paper, year by year

YearWhere it came up
2026Q4(f), Q11(c)
2025Q7
2024Q9
2023Q7
2022Q9
2021Q7
2019Q7
2018Q4(e), Q11(b)
2017Q9
2016Q4(e), Q10(a)

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

More Acids and bases questions

Acids and bases, 2 marks

Which of these is a conjugate acid-base pair?

  1. NH4+ and OH-
  2. H3O+ and OH-
  3. NH4+ and NH3
Show the answer

NH4+ and NH3

A conjugate pair differs by exactly one proton. NH4+ loses H+ to become NH3.

Acids and bases, 3 marks

Why can water act as both a Bronsted-Lowry acid and a base?

  1. Its pH is exactly 7 at all times
  2. It can donate or accept a proton
  3. It holds equal H+ and OH- ions only
Show the answer

It can donate or accept a proton

With HCl, water accepts a proton to form H3O+. With NH3, it donates one to form OH-. It is amphiprotic.

Acids and bases, 2 marks

In chemistry, the word concentrated describes?

  1. The amount of acid per litre
  2. How fully the acid ionises
  3. The pH at the end point
Show the answer

The amount of acid per litre

Concentration is how much is dissolved. Strength is how fully it ionises. A concentrated weak acid is possible.

Ordinary Level

Asked on 8 of the last 10 Ordinary Level papers, most recently in 2025. most years

Every paper, year by year

YearWhere it came up
2026Not asked
2025Q7
2024Q9
2023Q7
2022Q7
2021Not asked
2019Q9
2018Q10(a)
2017Q11(b)
2016Q10(b)

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

More Acids and bases questions

Acids and bases, 2 marks

Arrhenius definition of an acid?

  1. A substance that produces OH- ions in water
  2. A substance that accepts a proton
  3. A substance that produces H+ ions in water
Show the answer

A substance that produces H+ ions in water

For example HCl in water gives H+ and Cl- ions. Producing OH- ions is the Arrhenius definition of a base.

Acids and bases, 2 marks

Products when hydrochloric acid neutralises sodium hydroxide?

  1. Carbon dioxide and water
  2. A salt and water
  3. Hydrogen and a salt
Show the answer

A salt and water

HCl + NaOH gives NaCl + H2O. Hydrogen forms when an acid reacts with a metal.

Acids and bases, 2 marks

A strong acid is one that?

  1. Is almost fully dissociated (ionised) in water
  2. Is very concentrated, with little water present
  3. Has a high pH, above 7 on the scale
Show the answer

Is almost fully dissociated (ionised) in water

Strong means how fully it ionises, not how much is dissolved. A dilute solution of HCl is still a strong acid.

Other Chemistry topics

All of Leaving Cert Chemistry