Efficiency of the catalyst does not depend on its?

Options

A. Molecular weight
B. Number of free valencies
C. Physical state
D. Amount used

Explanation

To determine which factor the efficiency of a catalyst does not depend on, we need to analyze the options provided:

1. **Understanding Catalyst Efficiency**:
- The efficiency of a catalyst is measured in terms of its ability to convert reactants into products. It is quantified in "catal" (cat), where one cat is defined as the ability to convert one mole of reactant into product in one second.

2. **Factors Affecting Catalyst Efficiency**:
- The efficiency of a catalyst primarily depends on its **number of free valencies**. More free valencies mean that the catalyst can interact with more reactant molecules, thus increasing its efficiency.

3. **Analyzing the Options**:
- **A. Molecular Weight**: The molecular weight of a catalyst does not directly influence how effectively it can facilitate a reaction. Therefore, it does not affect the efficiency.
- **B. Number of Valencies**: This is a crucial factor that does affect the efficiency of the catalyst. More valencies lead to higher efficiency.
- **C. Physical State**: The physical state (solid, liquid, gas) of the catalyst can influence its interaction with reactants but does not determine its efficiency in terms of the rate of reaction.
- **D. Amount Used**: The amount of catalyst used can affect the total reaction rate but does not change the inherent efficiency of the catalyst itself.

4. **Conclusion**:
- The efficiency of a catalyst does not depend on its **molecular weight (A)**, **physical state (C)**, or **amount used (D)**. The correct answer is that the efficiency of a catalyst does not depend on its **molecular weight**.

### Final Answer:
The efficiency of the catalyst does not depend on its **molecular weight (A)**.