Chemistry 0620 · IGCSE · Reversible reactions and equilibrium

Reversible reactions and equilibrium — practice question

Ammonia, $\text{NH}_3$, dissolves in water to form a dilute ammonium hydroxide solution, $\text{NH}_4\text{OH}$. Because the reaction is reversible, the substances are present as an equilibrium mixture. $\text{NH}_3(g) + \text{H}_2\text{O}(l) \rightleftharpoons \text{NH}_4^+(aq) + \text{OH}^-(aq)$. Which statement regarding the mixture is correct?

  • AAll of the ammonia and water molecules have turned into ions.
  • BThe ammonia and water molecules have stopped changing into ions.
  • CThe concentrations of the ammonia molecules and ammonium ions are always equal.
  • DThe rate of the formation of ammonia molecules is equal to the rate of formation of the ammonium ions.

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