Question

Assertion (A): Transition metals and their complexes show catalytic activity.
Reason (R): The activation energy of a reaction is lowered by the catalyst.

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
• B. Both (A) and (R) are correct but (R) is not the correct explanation of (A)
• C. (A) is correct but (R) is incorrect
• D. (A) is incorrect but (R) is correct

Hint:

Transition metals act as catalysts mainly due to variable oxidation states and formation of intermediate complexes, which help in alternative reaction pathways.

Answer 1

The Correct Option is B

Step 1: Analyze Assertion (A).
Transition metals and their compounds are widely used as catalysts in many chemical reactions.
Examples include:
\[ Fe \rightarrow \text{Haber process} \] \[ V_2O_5 \rightarrow \text{Contact process} \] \[ Ni \rightarrow \text{Hydrogenation reactions} \] Transition metals show catalytic activity mainly because of:
Variable oxidation states and Ability to form intermediate complexes These properties help them provide an alternative reaction pathway.
Therefore, Assertion (A) is correct.

Step 2: Analyze Reason (R).
A catalyst increases the rate of a reaction by lowering the activation energy.
Activation energy is the minimum energy required for reactant molecules to undergo effective collision and form products.
By providing an alternative reaction pathway with lower activation energy, catalysts increase the reaction rate.
Hence, Reason (R) is also correct.

Step 3: Check whether Reason explains Assertion.
The reason states a general property of catalysts:
Catalysts lower activation energy However, the assertion specifically asks why transition metals and their complexes show catalytic activity.
The actual reason for catalytic activity of transition metals is their:
variable oxidation states and complex formation ability Thus, although the Reason is true, it does not specifically explain why transition metals are effective catalysts.
Therefore, Reason (R) is not the correct explanation of Assertion (A).

Step 4: Select the correct option.
Hence, the correct option is:
\[ (2)\;\text{Both (A) and (R) are correct but (R) is not the correct explanation of (A)} \]

Step 5: Final conclusion.
Therefore, the correct answer is:
\[ \boxed{\text{Both (A) and (R) are correct but (R) is not the correct explanation of (A)}} \]