When `NaNO_(3)` is heated in a closed vessel, oxygen is liberated and `NaNO_(2)` is left behind. At equilibrium, which are correct

Options

A. Addition of `NaNO_(2)` favours reverse reactions.
B. Addition of `NaNO_(2)` favours forward reactions.
C. Increasing temperature favours forward reaction
D. Increasing pressure reverse reaction.

Answer

To solve the problem regarding the decomposition of sodium nitrate (NaNO₃) when heated in a closed vessel, we need to analyze the equilibrium reaction and the effects of various changes on it.

### Step-by-Step Solution:

1. **Write the Reaction**:
The decomposition of sodium nitrate can be represented by the following chemical equation:
\[ 2 \text{NaNO}_3 (s) \rightarrow 2 \text{NaNO}_2 (s) + \text{O}_2 (g) \]
Here, solid sodium nitrate decomposes into solid sodium nitrite and gaseous oxygen.

2. **Identify the States of Matter**:
- NaNO₃ is a solid.
- NaNO₂ is a solid.
- O₂ is a gas.

3. **Analyze the Effect of Adding NaNO₂**:
- According to Le Chatelier's principle, adding a solid (NaNO₂) does not affect the equilibrium position because solids do not change the concentration in the same way that gases or liquids do.
- Therefore, the statement "addition of NaNO₂ favors the reverse reaction" is **incorrect**.

4. **Analyze the Effect of Increasing Temperature**:
- The reaction is endothermic since it requires heat to proceed (as indicated by the heating of NaNO₃).
- According to Le Chatelier's principle, increasing the temperature shifts the equilibrium towards the endothermic direction (forward reaction in this case).
- Thus, the statement "increase temperature favors forward reaction" is **correct**.

5. **Analyze the Effect of Increasing Pressure**:
- In this reaction, there are no gaseous reactants, but there is one mole of gaseous product (O₂).
- Increasing the pressure will shift the equilibrium towards the side with fewer moles of gas. Since the reactants (NaNO₃ and NaNO₂) are solids and do not contribute to the pressure, the reaction will shift to the left (reverse direction) to reduce the number of gas moles.
- Therefore, the statement "increasing pressure reverses the reaction" is **correct**.

### Conclusion:
Based on the analysis, the correct statements regarding the equilibrium are:
- C: "Increase temperature favors forward reaction" (Correct)
- D: "Increasing pressure reverses the reaction" (Correct)