`C(s) +H_2O(g) hArr CO(g) +H_2(g) , DeltaH lt 0`
the above equilibrium will proceed in forward direction when

Options

A. it is subjected to high pressure
B. it is subjected to high temperature
C. Inert gas (Argon) is added at constant pressure
D. Carbon (solid) is added

Answer

To determine when the equilibrium reaction \( C(s) + H_2O(g) \rightleftharpoons CO(g) + H_2(g) \) will proceed in the forward direction, we can analyze the conditions affecting the equilibrium based on Le Chatelier's principle and the thermodynamic properties of the reaction.

### Step-by-Step Solution

1. **Identify the Reaction Type**:
The reaction is given as:
\[ C(s) + H_2O(g) \rightleftharpoons CO(g) + H_2(g) \]
The reaction involves solid carbon and gaseous water producing gaseous carbon monoxide and hydrogen.

2. **Analyze the Change in Moles of Gas**:
- On the left side (reactants), we have 1 mole of \( H_2O(g) \) (1 mole of gas).
- On the right side (products), we have 1 mole of \( CO(g) \) and 1 mole of \( H_2(g) \) (2 moles of gas).
- Thus, the change in the number of moles of gas (\( \Delta n_g \)) is:
\[ \Delta n_g = (1 + 1) - 1 = 1 \]
Since \( \Delta n_g > 0 \), there are more moles of gas on the product side.

3. **Consider the Effect of Pressure**:
According to Le Chatelier's principle, if we increase the pressure, the equilibrium will shift towards the side with fewer moles of gas. Since the forward reaction produces more gas (2 moles) compared to the reactants (1 mole), increasing pressure will not favor the forward reaction. Therefore, the forward reaction will proceed under low pressure.

4. **Consider the Effect of Temperature**:
The reaction has a negative enthalpy change (\( \Delta H < 0 \)), indicating it is exothermic. For exothermic reactions, lowering the temperature favors the forward reaction. Thus, the forward reaction will proceed under low temperature conditions.

5. **Consider the Addition of Inert Gas**:
Adding an inert gas at constant pressure increases the volume of the system. This increase in volume effectively lowers the pressure. Since the forward reaction is favored at low pressure (as established), adding an inert gas will also favor the forward direction.

### Conclusion
The equilibrium will proceed in the forward direction when:
- The temperature is low (favoring exothermic reactions).
- The pressure is low (favoring the side with more gas moles).
- An inert gas is added at constant pressure (increasing volume and effectively lowering pressure).

Thus, the correct answer is that the equilibrium will proceed in the forward direction under low temperature and low pressure conditions, or when an inert gas is added at constant pressure.