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Leaving Cert Chemistry: Functional groups

How often Functional groups 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 2026. 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.

Functional groups, Higher Level(6 marks)

Quick ones on Functional groups.

(a)Name of the -COOH functional group?
  1. Carbonyl
  2. Carboxyl
  3. Hydroxyl
(b)Systematic name of CH3COOH?
  1. Ethanol
  2. Methanoic acid
  3. Ethanoic acid
(c)Functional group present in an aldehyde?
  1. -CHO
  2. -OH
  3. -COOH
Show the answers

(a) Carboxyl

(b) Ethanoic acid

(c) -CHO

Your turn: Higher Level questions on Functional groups.

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
2026Q11(a)
2025Q8
2024Q2, Q4(f), Q11(b)
2023Q4(i)
2022Q8, Q11(b)
2021Q4(j), Q8
2019Q2, Q8
2018Q8
2017Q8
2016Q2

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

More Functional groups questions

Functional groups, 3 marks

How does a ketone differ from an aldehyde?

  1. It has an -OH group joined to a carbon atom instead of a C=O group
  2. It contains a carbon to carbon double bond next to the C=O group
  3. Its C=O group is joined to two carbon atoms, not to a hydrogen
Show the answer

Its C=O group is joined to two carbon atoms, not to a hydrogen

Because there is no hydrogen on the carbonyl carbon, ketones are not readily oxidised, unlike aldehydes.

Functional groups, 3 marks

Why is ethanoic acid a much stronger acid than ethanol?

  1. Ethanoic acid is an ionic compound, so it is already split into ions
  2. The ethanoate ion is stabilised by resonance, which spreads its negative charge
  3. Ethanol has more hydrogen atoms, so each one is held more tightly by the molecule
Show the answer

The ethanoate ion is stabilised by resonance, which spreads its negative charge

The charge is shared over both oxygens, so losing H+ is easier. The C=O also pulls electrons from the O-H bond (inductive effect).

Functional groups, 2 marks

Which homologous series has the general formula CnH2n+1OH?

  1. Alcohols
  2. Aldehydes
  3. Carboxylic acids
Show the answer

Alcohols

An alkyl group joined to an -OH group, such as methanol CH3OH and ethanol C2H5OH, fits CnH2n+1OH.

Ordinary Level

Asked on 8 of the last 10 Ordinary Level papers, most recently in 2026. most years

Every paper, year by year

YearWhere it came up
2026Q8
2025Not asked
2024Q4(g), Q8
2023Q8
2022Q8
2021Not asked
2019Q8
2018Q8
2017Q8
2016Q8

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

More Functional groups questions

Functional groups, 2 marks

Typical smell of an ester?

  1. Like rotten eggs
  2. Like vinegar
  3. Sweet and fruity
Show the answer

Sweet and fruity

Esters are used in flavourings and perfumes. Vinegar smells of ethanoic acid, a carboxylic acid.

Functional groups, 2 marks

Functional group of an ester?

  1. -CHO
  2. -COO-
  3. -OH
Show the answer

-COO-

An ester link joins a carboxylic acid part and an alcohol part. -OH is an alcohol and -CHO an aldehyde.

Functional groups, 2 marks

Carboxylic acid found in ant stings and nettle stings?

  1. Methanoic acid
  2. Ethanoic acid
  3. Benzoic acid
Show the answer

Methanoic acid

Methanoic acid, HCOOH, is the simplest carboxylic acid. Ethanoic acid is in vinegar.

Other Chemistry topics

All of Leaving Cert Chemistry