Which of the following acts as a negative catalyst?

Options

A. Lead tetraethyl as an antiknock compound
B. Glycerol in decomposition of `H_(2)O_(2)`
C. Ethanol in the oxidation of chloroform
D. All the above

Answer

To determine which of the given compounds acts as a negative catalyst, we need to understand the definition and function of negative catalysts in chemical reactions. A negative catalyst is a substance that decreases the rate of a reaction without being consumed in the process.

### Step-by-Step Solution:

1. **Understand the Definition of Negative Catalyst:**
- A negative catalyst is a substance that slows down the rate of a chemical reaction. It does not change the mass or chemical composition at the end of the reaction.

2. **Analyze the Given Options:**
- We need to evaluate each of the given compounds to see if they act as negative catalysts.

3. **Option 1: Lead Tetraethyl**
- Lead tetraethyl is known as an anti-knock compound used in petrol. It decreases the ignition of petrol vapors, thus acting as a negative catalyst.
- **Conclusion:** Lead tetraethyl is a negative catalyst.

4. **Option 2: Glycerol**
- Glycerol can suppress the decomposition of hydrogen peroxide. By adding glycerol to hydrogen peroxide, the rate of decomposition is reduced, indicating that glycerol acts as a negative catalyst.
- **Conclusion:** Glycerol is a negative catalyst.

5. **Option 3: Ethanol**
- Ethanol is used in the oxidation of chloroform to terminate the formation of carbonyl chloride. A small amount of ethanol slows down this reaction, which means it acts as a negative catalyst.
- **Conclusion:** Ethanol is a negative catalyst.

6. **Final Conclusion:**
- Since all three options (Lead tetraethyl, Glycerol, and Ethanol) act as negative catalysts, we can conclude that the correct answer is that all the above options are negative catalysts.

### Final Answer:
All the given compounds (Lead tetraethyl, Glycerol, and Ethanol) act as negative catalysts.