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Difficulty: EasySalt Hydrolysis and Solution Acidity/Alkalinity

An aqueous solution of ammonium trioxonitrate(V), NH4NO3NH_4NO_3, turns blue litmus paper red. Which species and hydrolysis reaction account for this acidity?

  1. Cation hydrolysis where NH4+NH_4^+ reacts with water to produce H+H^+ ionsAnswer
  2. B
    Anion hydrolysis where NO3−NO_3^- reacts with water to produce OH−OH^- ions
  3. C
    Neutralization between NH4+NH_4^+ and NO3−NO_3^- ions in solution
  4. D
    Indicator interaction where NO3−NO_3^- directly alters litmus color without changing pH

Answer

Cation hydrolysis where NH4+NH_4^+ reacts with water to produce H+H^+ ions
The ammonium salt NH4NO3NH_4NO_3 is formed from a strong acid (HNO3HNO_3) and a weak base (NH3NH_3). Upon dissolving in water, the cation NH4+NH_4^+ reacts with water molecules (cation hydrolysis) according to the equilibrium NH4++H2O⇌NH3+H+NH_4^+ + H_2O ⇌ NH_3 + H^+. The generation of excess hydrogen ions makes the solution acidic and turns blue litmus red.

Step-by-Step Solution

1
Identify the parent acid and parent base of the salt
NH4NO3NH_4NO_3 is formed from a weak base (NH3NH_3) and a strong acid (HNO3HNO_3).
Salts formed from weak bases and strong acids dissolve in water to produce acidic solutions.
2
Determine which ion undergoes hydrolysis
The ammonium cation (NH4+NH_4^+) hydrolyzes: NH4+(aq)+H2O(l)⇌NH3(aq)+H+(aq)NH_4^+ (aq) + H_2O (l) ⇌ NH_3 (aq) + H^+ (aq).
The conjugate acid of a weak base is strong enough to react with water, whereas the conjugate anion of a strong acid (NO3−NO_3^-) is a spectator ion.
3
Relate ion generation to solution acidity
Production of excess H+H^+ ions turns blue litmus paper red.
Increased hydrogen ion concentration lowers pH below 7.

Key Concept

Hydrolysis of salts derived from strong acids and weak bases
Estimated Time:45s
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Topics

Salt Hydrolysis and Solution Acidity/Alkalinity

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