Ethylamine, C₂H₅NH₂, is an amine that dissolves in water to form an alkaline solution. Explain why ethylamine is described as a base and describe what would be observed when ethylamine solution is tested with damp red litmus paper. Then describe what happens when ethylamine reacts with hydrochloric acid, naming the type of reaction and the product formed.

WJEC A-Level Chemistry (Wales) — 4.6 Amines · Explain · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Ethylamine is a colourless gas at room temperature that readily dissolves in water. It belongs to the class of organic compounds called amines.

Model answer (5 marks)

Ethylamine is a base because it accepts a proton (H⁺) from water or an acid. The lone pair of electrons on the nitrogen atom is used to accept the proton.

When ethylamine solution is tested with damp red litmus paper, the paper turns blue.

The reaction between ethylamine and hydrochloric acid is a neutralisation reaction. The product formed is ethylammonium chloride (C₂H₅NH₃⁺Cl⁻).

Examiner tips

  • Use the term ‘accepts a proton’ to show basicity. Mention the lone pair on N. State the colour change of red litmus to blue. Identify the reaction as neutralisation and name the salt produced.
  • common_mistakes
  • :
  • Saying ethylamine is a base because it donates a proton. Forgetting to mention the lone pair on nitrogen. Describing the reaction as a synthesis rather than a neutralisation.

Mark scheme (5 marks)

  1. Ethylamine is a base because it accepts a proton / H⁺ (from water or an acid)
  2. The lone pair of electrons on the nitrogen atom is used to accept the proton
  3. Damp red litmus paper turns blue
  4. The reaction between ethylamine and hydrochloric acid is a neutralisation reaction
  5. The product is ethylammonium chloride / a salt (C₂H₅NH₃⁺Cl⁻)

Key terms in this question

amine · base

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