The equilibrium which remains unaffected by change in pressure of the reactants is

Options

A. `N_2(g)+O_2(g) iff 2NO(g)`
B. `2SO_2(g)+o_2(g) iff 2SO_3`
C. `2O_3(g) iff 3O_2(g)`
D. `2NO_2 iff N_2O_4`

Answer

To solve the question regarding which equilibrium remains unaffected by changes in pressure of the reactants, we need to analyze the concept of changes in pressure and how it affects chemical equilibria.

### Step-by-Step Solution:

1. **Understanding the Concept of Delta n**:
- Delta n (Δn) is defined as the change in the number of moles of gas during a reaction. It is calculated as the difference between the moles of gaseous products and the moles of gaseous reactants.
- Δn = (moles of gaseous products) - (moles of gaseous reactants).

2. **Effect of Pressure on Equilibrium**:
- According to Le Chatelier's principle, if the pressure of a system at equilibrium is changed, the equilibrium will shift in the direction that counteracts that change.
- If Δn = 0, meaning the number of moles of gas does not change during the reaction, then the equilibrium position will not be affected by changes in pressure.

3. **Analyzing the Given Options**:
- We need to check each option to find which one has Δn = 0.

**Option 1**: N₂(g) + O₂(g) ⇌ 2NO(g)
- Reactants: 1 (N₂) + 1 (O₂) = 2 moles
- Products: 2 (NO) = 2 moles
- Δn = 2 - 2 = 0 (This option is a candidate).

**Option 2**: 2SO₂(g) + O₂(g) ⇌ 2SO₃(g)
- Reactants: 2 (SO₂) + 1 (O₂) = 3 moles
- Products: 2 (SO₃) = 2 moles
- Δn = 2 - 3 = -1 (This option is not valid).

**Option 3**: 2O₃(g) ⇌ 3O₂(g)
- Reactants: 2 (O₃) = 2 moles
- Products: 3 (O₂) = 3 moles
- Δn = 3 - 2 = 1 (This option is not valid).

**Option 4**: 2NO₂(g) ⇌ N₂O₄(g)
- Reactants: 2 (NO₂) = 2 moles
- Products: 1 (N₂O₄) = 1 mole
- Δn = 1 - 2 = -1 (This option is not valid).

4. **Conclusion**:
- The only option where Δn = 0 is **Option 1**: N₂(g) + O₂(g) ⇌ 2NO(g). Therefore, this equilibrium remains unaffected by changes in pressure.

### Final Answer:
The equilibrium which remains unaffected by change in pressure of the reactants is **Option 1: N₂(g) + O₂(g) ⇌ 2NO(g)**.