Pressure is doubled in each of the following equilibrium . In which case yield is maximum ?

Options

A. `C(s)+H_(2)O(g) hArr CO(g)+H_(2)(g)`
B. `2H_(2)(g)+O_(2)(g) hArr 2H_(2)O(g)`
C. `2Fe(s)+3H_(2)O(g) hArr Fe_(2)O_(3)(s)+3H_(2)(g)`
D. `N_(2)O_(4)(g) hArr 2NO_(2)(g)`

Answer

To determine in which equilibrium the yield is maximized when the pressure is doubled, we can apply Le Chatelier's Principle. This principle states that if an equilibrium system is subjected to a change in pressure, temperature, or concentration, the system will adjust to counteract that change and restore a new equilibrium.

### Step-by-Step Solution:

1. **Identify the Equilibria**: We need to analyze the given equilibria to see how many moles of gas are present on both the reactant and product sides for each equilibrium.

2. **Count Moles of Gases**: For each equilibrium reaction, count the number of moles of gaseous reactants and products:
- **Equilibrium 1**: 1 mole of H2O (g) → 2 moles of products (g)
- Reactants: 1 mole
- Products: 2 moles
- **Equilibrium 2**: 2 moles of A (g) + 1 mole of B (g) → 2 moles of C (g)
- Reactants: 3 moles
- Products: 2 moles
- **Equilibrium 3**: 3 moles of D (g) ⇌ 3 moles of E (g)
- Reactants: 3 moles
- Products: 3 moles
- **Equilibrium 4**: 1 mole of F (g) → 2 moles of G (g)
- Reactants: 1 mole
- Products: 2 moles

3. **Apply Le Chatelier's Principle**: According to the principle, increasing the pressure will shift the equilibrium towards the side with fewer moles of gas:
- **Equilibrium 1**: Shift to the left (not favorable for yield).
- **Equilibrium 2**: Shift to the right (favorable for yield).
- **Equilibrium 3**: No shift (equal moles).
- **Equilibrium 4**: Shift to the right (favorable for yield).

4. **Determine Maximum Yield**:
- Equilibrium 2 and Equilibrium 4 both favor the forward direction when pressure is increased. However, Equilibrium 2 has a greater difference in moles (3 moles on reactants side vs. 2 moles on products side), thus it will shift more significantly towards the products.
- Therefore, the equilibrium that will yield the maximum product when pressure is doubled is **Equilibrium 2**.

### Conclusion:
The equilibrium with the maximum yield when pressure is doubled is **Equilibrium 2**.