Examkin

Question

Difficulty: EasySalt Hydrolysis and Solution Acidity/Alkalinity

Which of the following salts dissolves in water to form an alkaline solution that turns red litmus paper blue?

  1. Sodium trioxocarbonate(IV)Answer
  2. B
    Ammonium chloride
  3. C
    Sodium chloride
  4. D
    Potassium tetraoxosulfate(VI)

Answer

Sodium trioxocarbonate(IV) forms an alkaline solution in water due to anion hydrolysis.
Sodium trioxocarbonate(IV) dissolves in water to form sodium ions and trioxocarbonate(IV) ions. Because trioxocarbonate(IV) is the conjugate base of a weak acid, it reacts with water to release hydroxide ions (OH−OH^-), creating an alkaline solution that turns red litmus paper blue.

Step-by-Step Solution

1
Identify the parent acid and base for the salt.
Sodium trioxocarbonate(IV) (Na2CO3Na_2CO_3) is formed from sodium hydroxide (NaOHNaOH, a strong base) and carbonic acid (H2CO3H_2CO_3, a weak acid).
The hydrolysis behavior of a salt is determined by the relative strengths of its parent acid and base.
2
Analyze the ion hydrolysis reaction.
The carbonate anion (CO32−CO_3^{2-}) reacts with water according to: CO32−+H2O⇌HCO3−+OH−CO_3^{2-} + H_2O \rightleftharpoons HCO_3^- + OH^-.
Anions derived from weak acids act as conjugate bases and hydrolyze in water to generate hydroxide ions (OH−OH^-).
3
Determine the solution acidity/alkalinity and indicator response.
The production of excess OH−OH^- ions makes the solution basic (pH>7pH > 7), causing red litmus paper to turn blue.
Alkaline solutions contain a higher concentration of hydroxide ions than hydrogen ions, turning red litmus blue.

Key Concept

Salt Hydrolysis
Estimated Time:45s
Rate this question

Topics

Salt Hydrolysis and Solution Acidity/Alkalinity

More questions from this topic