AQA A-Level Chemistry Paper 3, 2023: Question 34

1 mark · Easy difficulty · Multiple Choice

Identifying the Strongest Base This question assesses the ability to compare the basicity of various compounds, including amines and ammonium salts. Factors affecting basicity, such as electron-donating groups, resonance, and the presence of acidic protons, should be considered. Recognising the influence of the compound's structure on its ability to accept protons is crucial.

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Question

AQA A-Level Chemistry Paper 3, 2023: Question 34
Question text

34 Which compound is the strongest base?

[1 mark]

A

B

C NH3

D NH4Cl

Mark scheme

Show the mark scheme Mark scheme for AQA A-Level Chemistry Paper 3, 2023: Question 34

34 A 1 (AO1)

How to answer it

Identifying the Strongest Base

Question

Which compound is the strongest base?

  • A: Cyclohexylamine ( C6H11NH2 )
  • B: Aniline ( C6H5NH2 )
  • C: Ammonia ( NH3 )
  • D: Ammonium chloride ( NH4Cl )

Correct Answer: A

The strongest base is cyclohexylamine ( C6H11NH2 ) . The electron-donating alkyl group increases the electron density on the nitrogen atom, making it a stronger base than the other compounds listed.

Teacher Tip: Explain how alkyl groups increase basicity by donating electrons to the nitrogen atom. Highlight why aromatic amines, like aniline, are weaker bases due to the delocalisation of the lone pair on nitrogen into the benzene ring.

Explanation of Other Options

  • B (Aniline): Weaker base because the lone pair on the nitrogen atom delocalises into the benzene ring, reducing its availability for protonation.
  • C (Ammonia): A moderate base, but less basic than cyclohexylamine, as it lacks electron-donating groups to enhance basicity.
  • D (Ammonium chloride): Not a base; it is the conjugate acid of ammonia and releases H+ in water.

Final Answer

The strongest base is:

A: Cyclohexylamine ( C6H11NH2 )

Topics

Organic Chemistry · 3.3.11 Amines

Question and mark scheme from the AQA A-Level Chemistry examination, Paper 3, 2023. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.