The catalyst used to increase the dissociation of `H_(2)O_(2)` is 

Options

A. Acetanilide
B. Glycerol
C. `H_(3)PO_(4)`
D. Caustic soda

Answer

To solve the question regarding the catalyst used to increase the dissociation of \( H_2O_2 \) (hydrogen peroxide), we will analyze the options provided and understand the role of catalysts in chemical reactions.

### Step-by-Step Solution:

1. **Understanding Catalysts**:
- A catalyst is a substance that increases or decreases the rate of a chemical reaction without being consumed in the process.
- There are two types of catalysts: positive catalysts (which increase the reaction rate) and negative catalysts (which decrease the reaction rate).

2. **Identifying the Reaction**:
- The reaction in question is the dissociation (decomposition) of hydrogen peroxide \( H_2O_2 \). This reaction can be represented as:
\[ 2 H_2O_2 \rightarrow 2 H_2O + O_2 \]

3. **Evaluating the Options**:
- The options given are:
- Acetylene light
- Glycerol
- \( H_3PO_4 \) (phosphoric acid)
- Caustic soda (NaOH)

4. **Analyzing Each Option**:
- **Acetylene light**: Generally used in various reactions but not specifically known as a catalyst for \( H_2O_2 \) decomposition.
- **Glycerol**: Typically acts as a solvent or stabilizer, not a catalyst for this reaction.
- **\( H_3PO_4 \)**: Phosphoric acid can act as a catalyst in some reactions but is not a positive catalyst for the decomposition of \( H_2O_2 \).
- **Caustic soda (NaOH)**: This is a strong base and acts as a positive catalyst that increases the rate of decomposition of hydrogen peroxide by providing hydroxide ions which facilitate the breakdown of the peroxyl linkage.

5. **Conclusion**:
- Among the options provided, **caustic soda (NaOH)** is the correct answer as it is a positive catalyst that increases the dissociation of \( H_2O_2 \).

### Final Answer:
The catalyst used to increase the dissociation of \( H_2O_2 \) is **caustic soda (NaOH)**.