Bronsted-Lowry acids and basesAQA A-Level Chemistry: Mind map

Exam questions on Bronsted-Lowry acids and bases

1. Ammonia gas dissolves in water to form a solution that turns red litmus blue. The equilibrium in the solution can be written as NH₃ + H₂O ⇌ NH₄⁺ + OH⁻.
   Explain, in terms of proton transfer, why ammonia acts as a base in water.2 marks
2. Sodium hydrogencarbonate is added to water. The hydrogencarbonate ion, HCO₃⁻, reacts with acids and with alkalis according to the equations: (1) HCO₃⁻ + H₃O⁺ → H₂CO₃ + H₂O and (2) HCO₃⁻ + OH⁻ → CO₃²⁻ + H₂O.
   Use the two equations to explain why the hydrogencarbonate ion can act as both an acid and a base.2 marks
3. Two acid–base reactions are studied. Reaction 1: hydrogen chloride gas and ammonia gas meet in a dry tube and form a white smoke of solid ammonium chloride, HCl(g) + NH₃(g) → NH₄Cl(s). Reaction 2: in the nitrating mixture used to make nitrobenzene, concentrated nitric acid is mixed with concentrated sulfuric acid, HNO₃ + H₂SO₄ ⇌ H₂NO₃⁺ + HSO₄⁻.
   Explain, in terms of proton transfer, why Reaction 1 is an acid–base reaction, identifying the acid and the base.3 marks