NaNO2 is the salt of strong base NaOH and weak acid HNO2, on hydrolysis NaNO2 + H2O –> HNO2 + NaOH since NaOH is a stronger base compare to weak acid HNO2. Hence the aqueous solution of NaNO2 shows basic. 2). HNO2 is a weak.
The correct answer and explanation is:
Correct Answer and Explanation:
Sodium nitrite (NaNO₂) is a salt formed from the strong base sodium hydroxide (NaOH) and the weak acid nitrous acid (HNO₂). When NaNO₂ dissolves in water, it undergoes hydrolysis, as follows: NaNO2+H2O⇌HNO2+NaOH\text{NaNO}_2 + \text{H}_2\text{O} \rightleftharpoons \text{HNO}_2 + \text{NaOH}
Since NaOH is a strong base and HNO₂ is a weak acid, the solution becomes basic. The hydroxide ions (OH⁻) released by NaOH dominate over the hydrogen ions (H⁺) released by HNO₂, resulting in a pH greater than 7.
Explanation:
- Nature of the Components:
- NaOH (Sodium Hydroxide): A strong base that fully dissociates in water, producing Na⁺ and OH⁻ ions.
- HNO₂ (Nitrous Acid): A weak acid that only partially dissociates, releasing a limited number of H⁺ ions.
- NaNO₂ (Sodium Nitrite): The salt of a strong base (NaOH) and a weak acid (HNO₂).
- Hydrolysis of Sodium Nitrite:
- When NaNO₂ dissolves in water, it dissociates into sodium ions (Na⁺) and nitrite ions (NO₂⁻).
- The Na⁺ ion does not undergo hydrolysis, as it is a spectator ion.
- The NO₂⁻ ion, derived from the weak acid HNO₂, reacts with water to form OH⁻ ions:
- Effect on pH:
- Since OH⁻ ions increase in the solution, the pH of NaNO₂ solution is greater than 7.
- The presence of excess hydroxide ions confirms the basic nature of the solution.
- Conclusion:
- Since the base NaOH is stronger than the acid HNO₂, the hydrolysis of NaNO₂ results in a basic solution.
- This is a classic example of how the salt of a strong base and a weak acid produces a basic solution upon hydrolysis.