The efficiency of a catalyst depend on its

Options

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

Answer

To solve the question regarding the efficiency of a catalyst, we can break down the information provided in the video transcript into a step-by-step explanation.

### Step-by-Step Solution:

1. **Understanding Catalysts**: A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. Its efficiency is crucial for many industrial processes.

2. **Role of Surface Area**: The efficiency of a catalyst is significantly influenced by its surface area. A larger surface area allows for more active sites where reactions can occur.

3. **Active Centers**: The catalyst surface is not uniform; it has areas known as active centers where the concentration of free bonds is higher. These active centers are typically found at peaks, cracks, and corners of the catalyst.

4. **Adsorption of Reactants**: The catalytic activity is largely due to the adsorption of reacting molecules at these active centers. The efficiency of the catalyst increases when more reactant molecules can adsorb onto these active sites.

5. **Free Valences**: The number of free valences (or available bonds) at the active centers is critical. More free valences mean a higher probability of reactant molecules being activated and adsorbed, leading to an increased rate of reaction.

6. **Conclusion**: Therefore, the efficiency of a catalyst depends on the number of free valences available at its active centers. This leads us to conclude that the correct option regarding the efficiency of a catalyst is related to the number of free valences.

### Final Answer:
The efficiency of a catalyst depends on the number of free valences.