The reaction `NH_(4)^(+)+CN rarr HCN(aq)+NH_(3)(aq)` proceeds in

Options

A. Forward direction
B. Backward direction
C. In both sides
D. Can not be predicted

Answer

To determine the direction in which the reaction \( \text{NH}_4^+ + \text{CN}^- \rightleftharpoons \text{HCN} + \text{NH}_3 \) proceeds, we need to analyze the behavior of the reactants and products in aqueous solution.

### Step-by-Step Solution:

1. **Write the Reaction**:
The given reaction is:
\[ \text{NH}_4^+ + \text{CN}^- \rightleftharpoons \text{HCN} + \text{NH}_3 \]

2. **Identify the Species**:
In this reaction, we have:
- Reactants: Ammonium ion (\( \text{NH}_4^+ \)) and cyanide ion (\( \text{CN}^- \))
- Products: Hydrogen cyanide (\( \text{HCN} \)) and ammonia (\( \text{NH}_3 \))

3. **Consider the Properties of Ammonia and Ammonium Ion**:
- Ammonia (\( \text{NH}_3 \)) is a weak base and can dissolve in water to form ammonium ions (\( \text{NH}_4^+ \)):
\[ \text{NH}_3 + \text{H}_2\text{O} \rightleftharpoons \text{NH}_4^+ + \text{OH}^- \]
This reaction increases the concentration of \( \text{NH}_4^+ \) in solution, contributing to a basic environment.

4. **Effect of Basic Conditions on Cyanide Ion**:
- Under basic conditions, hydrogen cyanide (\( \text{HCN} \)) exists predominantly as cyanide ions (\( \text{CN}^- \)):
\[ \text{HCN} \rightleftharpoons \text{H}^+ + \text{CN}^- \]
Therefore, in a basic solution, the equilibrium shifts towards the formation of \( \text{CN}^- \).

5. **Determine the Direction of the Reaction**:
- Since ammonia increases the concentration of \( \text{NH}_4^+ \) and the basic conditions favor the formation of \( \text{CN}^- \), the reaction will proceed in the backward direction to re-establish equilibrium:
\[ \text{NH}_4^+ + \text{CN}^- \leftarrow \text{HCN} + \text{NH}_3 \]

6. **Conclusion**:
The reaction proceeds in the backward direction.

### Final Answer:
The reaction \( \text{NH}_4^+ + \text{CN}^- \rightleftharpoons \text{HCN} + \text{NH}_3 \) proceeds in the backward direction.

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