A Levels Chemistry (9701)•9701/13/M/J/19
Explanation
Acid-Base Properties of NH4+
Steps:
- Identify NH4+ as the conjugate acid of NH3, which donates a proton in reactions.
- Test option A: NH4+ donates H+, acting as an acid, not a base.
- Test option B: NH4+ reacts with OH- via NH4+ + OH- → NH3 + H2O, confirming correctness.
- Test options C and D: Recall NH4+ geometry as tetrahedral with sp3 hybridization and 109.5° angles.
Why B is correct:
- NH4+ is a weak acid that deprotonates in the presence of OH-, forming ammonia per the reaction NH4+ + OH- → NH3 + H2O.
Why the others are wrong:
- A: NH4+ donates protons, making it a Brønsted-Lowry acid, not a base.
- C: NH4+ is tetrahedral with 109.5° bond angles; pyramidal 107° describes NH3.
- D: Nitrogen in NH4+ uses sp3 hybridization for four sigma bonds.
Final answer: B
Topic: Nitrogen and sulfur
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