In which of the following reactions heterogeneous catalysis is involved?
(i) `2SO_2(g) + O_2(g) overset(NO(g))to 2SO_3(g)`
(ii) `2SO_2 (g) + O_2(g) overset(Pt(s))to 2SO_3(g)`
(iii) `N_2(g) + 3H_2(g) overset(Fe(s))to 2NH_3(g)`
(iv) `CH_3COOCH_3(l) + H_2O(g) overset(HCl(l))to CH_3COOH(aq) + CH_3OH (aq)`
options- a). (i), (iii)
b) (ii), (iii), (iv)
c) (i), (ii), (iii)
d) (iv)

Options

A. (i), (iii)
B. (ii), (iii), (iv)
C. (i), (ii), (iii)
D. (iv)

Answer

To determine which of the given reactions involve heterogeneous catalysis, we first need to understand the definitions of homogeneous and heterogeneous catalysis:

1. **Homogeneous Catalysis**: This occurs when the catalyst and the reactants are in the same phase (i.e., all gases, all liquids, or all solids).
2. **Heterogeneous Catalysis**: This occurs when the catalyst is in a different phase than the reactants.

Now, let's analyze each reaction step by step:

### Step 1: Analyze Reaction (i)
- **Reaction**: `2SO_2(g) + O_2(g) overset(NO(g))to 2SO_3(g)`
- **States**: Both reactants (SO2 and O2) are gases, and the catalyst (NO) is also a gas.
- **Conclusion**: Since all species are in the same phase (gas), this is **homogeneous catalysis**.

### Step 2: Analyze Reaction (ii)
- **Reaction**: `2SO_2(g) + O_2(g) overset(Pt(s))to 2SO_3(g)`
- **States**: The reactants (SO2 and O2) are gases, and the catalyst (Pt) is a solid.
- **Conclusion**: Since the catalyst is in a different phase (solid) from the reactants (gases), this is **heterogeneous catalysis**.

### Step 3: Analyze Reaction (iii)
- **Reaction**: `N_2(g) + 3H_2(g) overset(Fe(s))to 2NH_3(g)`
- **States**: The reactants (N2 and H2) are gases, and the catalyst (Fe) is a solid.
- **Conclusion**: Since the catalyst is in a different phase (solid) from the reactants (gases), this is **heterogeneous catalysis**.

### Step 4: Analyze Reaction (iv)
- **Reaction**: `CH_3COOCH_3(l) + H_2O(g) overset(HCl(l))to CH_3COOH(aq) + CH_3OH(aq)`
- **States**: The reactants are in different phases: CH3COOCH3 is a liquid, H2O is a gas, and the catalyst (HCl) is also a liquid.
- **Conclusion**: Since the reactants and catalyst are not all in the same phase (liquid and gas), this is **heterogeneous catalysis**.

### Final Conclusion
Based on the analysis:
- Reaction (i) is homogeneous.
- Reactions (ii), (iii), and (iv) are heterogeneous.

Thus, the correct answer is:
**Option b) (ii), (iii), (iv)**.