In which of the following reaction the increase in pressure will favour the increase in products ?

Options

A. `N_(2(g))+O_(2(g))hArr2NO_((g))`
B. `PCl_(3(g))+Cl_(2(g))hArrPCl_(5(g))`
C. `PCl_(5(g))hArrPCl_(3(g))+Cl_(2(g))`
D. `2CO_(2(g))hArr2CO_((g))+O_(2(g))`

Explanation

To determine in which reaction an increase in pressure will favor the formation of products, we can use 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 restore a new equilibrium.

### Step-by-Step Solution:

1. **Identify the Reactions**: We need to analyze each reaction option provided to see the number of gaseous moles on both the reactant and product sides.

2. **Apply Le Chatelier's Principle**: According to the principle, increasing pressure will favor the side of the reaction with fewer moles of gas. Therefore, we need to compare the total number of moles of gaseous reactants and products.

3. **Analyze Each Option**:
- **Option A**:
- Reactants: 1 mole of N₂ + 1 mole of O₂ = 2 moles
- Products: 2 moles (assumed from the context)
- Conclusion: No change in moles. Pressure change does not favor either side.

- **Option B**:
- Reactants: 2 moles (assumed from the context)
- Products: 1 mole of PCl₅
- Conclusion: Fewer moles on the product side (1 mole), so increasing pressure favors the formation of products.

- **Option C**:
- Reactants: 1 mole (assumed from the context)
- Products: 2 moles
- Conclusion: More moles on the product side, so increasing pressure favors the reactants.

- **Option D**:
- Reactants: 2 moles (assumed from the context)
- Products: 3 moles
- Conclusion: More moles on the product side, so increasing pressure favors the reactants.

4. **Final Conclusion**: The only reaction where increasing pressure favors the formation of products is **Option B**, where the number of gaseous moles on the product side is less than that on the reactant side.

### Answer:
**Option B** is the correct answer, as an increase in pressure will favor the formation of products.

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