In which of the following reaction, the yield of the products does not increase by increase in thepressure?

Options

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

Explanation

To determine in which of the following reactions the yield of the products does not increase with an increase in pressure, we can apply Le Chatelier's principle. This principle states that if a system at equilibrium is subjected to a change in pressure, temperature, or concentration, the system will adjust to counteract that change and establish a new equilibrium.

### Step-by-Step Solution:

1. **Understand the Principle**: According to Le Chatelier's principle, increasing the pressure will favor the side of the reaction with fewer moles of gas. Therefore, we need to analyze the number of moles of gas on both sides of the reactions provided.

2. **Analyze Each Reaction**:
- **Reaction 1**: \( N_2(g) + O_2(g) \rightleftharpoons 2NO(g) \)
- Reactants: 1 mole of \( N_2 \) + 1 mole of \( O_2 \) = 2 moles
- Products: 2 moles of \( NO \)
- **Conclusion**: No change in moles (2 moles on both sides). Therefore, increasing pressure does not affect the yield.

- **Reaction 2**: \( 2SO_2(g) + O_2(g) \rightleftharpoons 2SO_3(g) \)
- Reactants: 2 moles of \( SO_2 \) + 1 mole of \( O_2 \) = 3 moles
- Products: 2 moles of \( SO_3 \)
- **Conclusion**: Decrease in moles (3 moles to 2 moles). Increasing pressure will favor the formation of \( SO_3 \).

- **Reaction 3**: \( N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g) \)
- Reactants: 1 mole of \( N_2 \) + 3 moles of \( H_2 \) = 4 moles
- Products: 2 moles of \( NH_3 \)
- **Conclusion**: Decrease in moles (4 moles to 2 moles). Increasing pressure will favor the formation of \( NH_3 \).

- **Reaction 4**: \( PCl_3(g) + Cl_2(g) \rightleftharpoons PCl_5(g) \)
- Reactants: 1 mole of \( PCl_3 \) + 1 mole of \( Cl_2 \) = 2 moles
- Products: 1 mole of \( PCl_5 \)
- **Conclusion**: Decrease in moles (2 moles to 1 mole). Increasing pressure will favor the formation of \( PCl_5 \).

3. **Final Conclusion**: The only reaction where the yield of the product does not increase with an increase in pressure is the first reaction:
\[ N_2(g) + O_2(g) \rightleftharpoons 2NO(g) \]

### Answer:
The yield of the products does not increase by an increase in pressure in the reaction:
\[ N_2(g) + O_2(g) \rightleftharpoons 2NO(g) \]