Pure ammonia is placed in a vessel at a temperature where its dissociation constant (`alpha`) is appreciable. At equilibrium, `N_(2) + 3H_(2) rarr 2NH_(3)`

Options

A. `K_(p)` does not change significantly with pressure
B. `alpha` does not change with pressure
C. concentration of `NH_(3)` does not change with pressure
D. concentration of hydrogen is less than that of nitrogen

Explanation

To solve the problem regarding the dissociation of ammonia at equilibrium, we need to analyze the given reaction and the implications of the dissociation constant (α) being appreciable.

### Step-by-Step Solution:

1. **Understanding the Reaction**:
The reaction given is:
\[ N_2 + 3H_2 \rightleftharpoons 2NH_3 \]
This indicates that nitrogen and hydrogen gases combine to form ammonia.

2. **Equilibrium Constant Expression**:
The equilibrium constant \( K_p \) for the reaction can be expressed as:
\[ K_p = \frac{(P_{NH_3})^2}{(P_{N_2})(P_{H_2})^3} \]
where \( P_{NH_3} \), \( P_{N_2} \), and \( P_{H_2} \) are the partial pressures of ammonia, nitrogen, and hydrogen, respectively.

3. **Effect of Temperature**:
It is stated that the dissociation constant \( \alpha \) is appreciable, which implies that the equilibrium position is significantly shifted towards the reactants (N2 and H2). However, \( K_p \) is only affected by temperature and not by changes in pressure or concentration.

4. **Pressure and Kp**:
According to Le Chatelier's principle, while changes in pressure can affect the position of equilibrium, the value of \( K_p \) itself remains constant at a given temperature. Therefore, the statement that \( K_p \) does not change significantly with pressure is true.

5. **Conclusion**:
Since the question asks about the behavior of \( K_p \) and its dependence on temperature, we conclude that the correct option is that \( K_p \) does not change significantly with pressure.

### Final Answer:
The correct statement regarding the dissociation of ammonia at equilibrium is that \( K_p \) does not change significantly with pressure; it depends only on temperature.

---