Ethylamine (CH₃CH₂NH₂) is a primary amine. Explain how ethylamine acts as a base when it reacts with dilute hydrochloric acid, and describe the type of salt produced.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Amines are organic compounds derived from ammonia in which one or more hydrogen atoms have been replaced by alkyl or aryl groups. Like ammonia, primary amines can act as bases.
Model answer (5 marks)
Ethylamine acts as a base by donating a lone pair of electrons on the nitrogen atom.
The lone pair accepts a proton (H⁺) from the hydrochloric acid.
This gives the ethylammonium ion, CH₃CH₂NH₃⁺.
The chloride ion (Cl⁻) from HCl associates with the ethylammonium ion to form the salt.
The salt is an alkylammonium chloride, i.e. ethylammonium chloride, an ammonium salt.
The lone pair accepts a proton (H⁺) from the hydrochloric acid.
This gives the ethylammonium ion, CH₃CH₂NH₃⁺.
The chloride ion (Cl⁻) from HCl associates with the ethylammonium ion to form the salt.
The salt is an alkylammonium chloride, i.e. ethylammonium chloride, an ammonium salt.
Examiner tips
- Show the electron‑pair donation and proton acceptance clearly. Name the salt correctly as ethylammonium chloride. Mention that it is an ammonium (alkylammonium) salt. Use the term ‘donates a lone pair’ to hit the key phrase.
Common mistakes
- Writing that ethylamine *accepts* a proton instead of donating a lone pair. Forgetting to name the salt as ethylammonium chloride. Calling the salt a ‘neutral’ salt instead of an ammonium salt.
Mark scheme (5 marks)
- Ethylamine acts as a base by donating a lone pair of electrons (from the nitrogen atom)
- The lone pair accepts a proton (H⁺) from the hydrochloric acid
- This forms an ammonium-type ion / ethylammonium ion (CH₃CH₂NH₃⁺)
- The salt produced is an ionic compound / named correctly as ethylammonium chloride
- The salt is an ammonium salt (an alkylammonium salt), analogous to the salt formed when ammonia reacts with an acid
Key terms in this question
Related
- All Edexcel A-Level Chemistry (9CH0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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