Which of the following catalysts is not correctly matched with the reaction ?

Options

A. Vanadium (V) oxide in contact process for oxidation of `SO_2" to"SO_3`.
B. Finely divided iron in Haber's process in converion of `N_2and H_2" to " NH_3`.
C. `PtCl_2` catalyses the oxidation of ethyne to ethanal in the Wacker process.
D. Ni in presence of hydrogen for conversion of vegetable oil to ghee.

Explanation

To determine which catalyst is not correctly matched with its corresponding reaction, we will analyze each option provided.

### Step-by-Step Solution:

1. **Option 1: Vanadium Oxide in Contact Process for Oxidation of SO2 to SO3**
- Vanadium pentoxide (V2O5) is indeed used as a catalyst in the contact process for the oxidation of sulfur dioxide (SO2) to sulfur trioxide (SO3). This process is essential in the manufacture of sulfuric acid (H2SO4).
- **Conclusion:** This option is correctly matched.

2. **Option 2: Finely Divided Iron in Haber Process for Conversion of N2 and H2 to NH3**
- The Haber process involves the synthesis of ammonia (NH3) from nitrogen (N2) and hydrogen (H2) gas, using finely divided iron as a catalyst.
- **Conclusion:** This option is also correctly matched.

3. **Option 3: PtCl2 Catalyzes the Oxidation of Ethylene to Ethanol in the Wacker Process**
- The Wacker process actually uses palladium chloride (PdCl2) as the catalyst to oxidize ethylene (C2H4) to acetaldehyde (CH3CHO), not ethanol. The statement mentions PtCl2, which is incorrect as PtCl2 is not used in this process.
- **Conclusion:** This option is not correctly matched.

4. **Option 4: Nickel in Presence of Hydrogen for Conversion of Vegetable Oil to Ghee**
- Nickel is used as a catalyst in the hydrogenation of vegetable oils to convert them into solid fats (ghee). This process is indeed correct.
- **Conclusion:** This option is correctly matched.

### Final Answer:
The catalyst that is not correctly matched with the reaction is **Option 3: PtCl2 catalyzes the oxidation of ethylene to ethanol in the Wacker process**.

---