Assertion :- Catalyst is more effective in powdered form.
Reason :- Number of free valencies increase.

Options

A. If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion.
B. If both Assertion & Reason are True but Reason is not a correct explanation of the Assertion.
C. If Assertion is True but the Reason is False.
D. If both Assertion & Reason are False.

Answer

To solve the question regarding the assertion and reason about catalysts, we will break down the concepts step by step.

### Step 1: Understand the Assertion
The assertion states: "Catalyst is more effective in powdered form."
- A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. Its effectiveness can depend on its surface area.

**Hint:** Think about how the physical form of a catalyst can influence its ability to interact with reactants.

### Step 2: Analyze the Reason
The reason given is: "Number of free valencies increase."
- Free valencies refer to the available sites on the catalyst where reactants can attach. In powdered form, the catalyst has a larger surface area, which means more sites are available for reactants to interact.

**Hint:** Consider how the physical state of a substance can affect its surface area and the number of active sites available for reactions.

### Step 3: Relate Assertion and Reason
- When a catalyst is in powdered form, its surface area increases significantly compared to its bulk form. This increased surface area allows more reactant molecules to come into contact with the catalyst, enhancing the reaction rate.
- Additionally, the increase in the number of free valencies means that there are more active sites available for the reactants to attach, further increasing the effectiveness of the catalyst.

**Hint:** Reflect on how surface area and active sites contribute to the efficiency of a catalyst in a chemical reaction.

### Step 4: Conclusion
Both the assertion and the reason are true. The reason provided correctly explains why the assertion is valid. Therefore, the answer is that both the assertion and reason are true, and the reason is a correct explanation of the assertion.

**Final Answer:** Both assertion and reason are true, and the reason is the correct explanation for the assertion.