Question

At room temperature, disproportionation of an aqueous solution of in situ generated nitrous acid (HNO₂) gives the species

• A. H₃O⁺, NO₃^- and NO
• B. H₃O⁺, NO₃^- and NO₂
• C. H₂O⁺, NO^- and NO₂
• D. H₃O⁺, NO₃^- and N₂O

Answer 1

The Correct Option is A

To solve the problem, we need to identify the species produced during the disproportionation of aqueous nitrous acid (HNO₂) at room temperature.

1. Understanding Disproportionation of HNO₂:
Disproportionation is a redox reaction where a single species undergoes both oxidation and reduction. In the case of nitrous acid (HNO₂), it can disproportionate as:

\[ 3 \, \text{HNO}_2 \rightarrow \text{HNO}_3 + 2 \, \text{NO} + \text{H}_2\text{O} \]

This reaction produces nitric acid (HNO₃), nitric oxide (NO), and water.

2. Ionic forms in aqueous medium:
- Nitric acid dissociates into hydronium ion (H₃O⁺) and nitrate ion (NO₃^-).
- Nitric oxide (NO) remains as a gas.

3. Therefore, species formed are:
\[ \text{H}_3\text{O}^+, \quad \text{NO}_3^-, \quad \text{NO} \]

Final Answer:
H₃O⁺, NO₃^-, and NO.

Answer 2

To determine the products of the disproportionation of nitrous acid (HNO₂) at room temperature, we must consider the typical behavior of nitrous acid when it undergoes disproportionation. Disproportionation is a type of redox reaction where a single substance is simultaneously oxidized and reduced, resulting in the formation of two different products. For nitrous acid, the disproportionation reaction can be represented as follows:

3 HNO₂(aq) → H₃O⁺(aq) + 2 NO(g) + NO₃^-(aq)

In this reaction:

• HNO₂ is oxidized to NO₃^-
• HNO₂ is reduced to NO
• Additionally, H₃O⁺ ions are generated to maintain the charge balance

This matches the result in the first option: H₃O⁺, NO₃^- and NO. The correct disproportionation products are therefore identified, confirming that the generated species are hydronium ions, nitrate ions, and nitric oxide.