Choose the correct statement about the equilibrium
`A(s)+2B(g)hArrC(g)+D(g)`

Options

A. change in temp. changes both the state of eqb. and the eqb. constant
B. change in pressure changes both the state of eqb. and the eqb. constant
C. change in temperature changes eqb. constant but not the state of eqb.
D. change in pressure does not affect either eqb. constant or state of eqb.

Answer

To analyze the equilibrium reaction \( A(s) + 2B(g) \rightleftharpoons C(g) + D(g) \), we will consider the effects of temperature and pressure on the equilibrium constant and the position of equilibrium.

### Step-by-Step Solution:

1. **Identify the Nature of the Reaction**:
- The reaction involves a solid \( A \) and gaseous reactants and products. The solid does not appear in the equilibrium expression.

2. **Equilibrium Constant Expression**:
- The equilibrium constant \( K_c \) for the reaction can be expressed as:
\[ K_c = \frac{[C][D]}{[B]^2} \]
- Note that the concentration of solid \( A \) does not appear in the expression.

3. **Effect of Temperature on Equilibrium Constant**:
- If the reaction is endothermic, increasing the temperature will increase \( K_c \). Conversely, for an exothermic reaction, increasing the temperature will decrease \( K_c \).
- Therefore, temperature changes will affect the equilibrium constant.

4. **Effect of Temperature on Position of Equilibrium**:
- For an endothermic reaction, increasing the temperature shifts the equilibrium to the right (towards products). For an exothermic reaction, it shifts to the left (towards reactants).
- Thus, temperature changes will also affect the position of equilibrium.

5. **Effect of Pressure on Equilibrium**:
- Changes in pressure primarily affect gaseous reactions. For the given reaction, if the pressure is increased, the equilibrium will shift towards the side with fewer moles of gas.
- In this case, the left side has 2 moles of gas (from \( 2B(g) \)) and the right side has 2 moles of gas (from \( C(g) + D(g) \)). Therefore, changes in pressure will not affect the position of equilibrium since the number of moles of gas is the same on both sides.

6. **Conclusion**:
- The correct statement about the equilibrium is that temperature changes affect both the equilibrium constant and the position of equilibrium, while pressure changes do not affect the equilibrium constant but can affect the position of equilibrium depending on the number of moles of gas.

### Final Answer:
The correct statement is: "Change in temperature affects both the equilibrium constant and the position of equilibrium, while change in pressure does not affect the equilibrium constant."