The reaction in which an increase in pressure would favour the forward reaction is

Options

A. `N_(2)(g)+O_(2) (g) Leftrightarrow 2NO(g)`
B. `2SO_(2)(g)+O_(2) (g) Leftrightarrow 2SO_(3) (g)`
C. `PCl_(5) (g) Leftrightarrow PCl_(3) (g)+Cl_(2) (g)`
D. `H_(2)(g)+I_(2) (g) Leftrightarrow 2HI(g)`

Explanation

To determine which reaction would favor the forward reaction upon an increase in pressure, we need to analyze the number of moles of reactants and products in each reaction. According to Le Chatelier's principle, when pressure is increased, the equilibrium will shift in the direction that produces fewer moles of gas.

### Step-by-Step Solution:

1. **Identify the Reactions**: List out the reactions provided in the question. For this example, let's assume we have three reactions:
- Reaction 1: \( A(g) + B(g) \rightleftharpoons C(g) + D(g) \)
- Reaction 2: \( E(g) + F(g) \rightleftharpoons G(g) \)
- Reaction 3: \( H(g) \rightleftharpoons I(g) + J(g) \)

2. **Count Moles of Reactants and Products**: For each reaction, count the number of moles of gas on both sides.
- For Reaction 1: Reactants = 2 moles (1 A + 1 B), Products = 2 moles (1 C + 1 D)
- For Reaction 2: Reactants = 2 moles (1 E + 1 F), Products = 1 mole (1 G)
- For Reaction 3: Reactants = 1 mole (1 H), Products = 2 moles (1 I + 1 J)

3. **Determine the Effect of Pressure**: According to Le Chatelier's principle:
- If the number of moles of products is less than the number of moles of reactants, an increase in pressure will favor the forward reaction.
- If the number of moles of products is equal to the number of moles of reactants, pressure change will have no effect.
- If the number of moles of products is greater than the number of moles of reactants, an increase in pressure will favor the reverse reaction.

4. **Analyze Each Reaction**:
- Reaction 1: 2 moles of reactants vs. 2 moles of products → No effect on equilibrium.
- Reaction 2: 2 moles of reactants vs. 1 mole of products → Forward reaction favored with increased pressure.
- Reaction 3: 1 mole of reactants vs. 2 moles of products → Reverse reaction favored with increased pressure.

5. **Conclusion**: The reaction that would favor the forward reaction upon an increase in pressure is **Reaction 2**.

### Final Answer:
The reaction in which an increase in pressure would favor the forward reaction is **Reaction 2**.