Which of the following factors are responsible for the increase in the rate of a surface catalysed reaction?
(i) A catalyst provides proper orientation for the reactant molecules to react.
(ii) heat of adsorption of reactants on a catalyst helps reactant molecules to overcome activation energy.
(iii) The catalyst increases the activation energy of the reactio.

Options

A. (i) and (iii)
B. (i) and (ii)
C. (ii) and (iii)
D. (i),(ii) and (iii)

Explanation

To determine which factors are responsible for the increase in the rate of a surface-catalyzed reaction, we will analyze each statement provided in the question.

### Step 1: Analyze the first statement
**Statement (i): A catalyst provides proper orientation for the reactant molecules to react.**

A catalyst indeed plays a crucial role in orienting reactant molecules correctly. This proper orientation allows the reactants to collide in an effective manner, increasing the likelihood of a successful reaction. This is often described using the "lock and key" model, where the catalyst provides a specific site for the reactants to bind, facilitating the reaction.

**Conclusion:** This statement is **correct**.

### Step 2: Analyze the second statement
**Statement (ii): Heat of adsorption of reactants on a catalyst helps reactant molecules to overcome activation energy.**

The heat of adsorption refers to the energy released when reactants adhere to the surface of the catalyst. This process can lower the overall activation energy required for the reaction to occur. By providing energy through adsorption, the catalyst helps the reactants to reach the transition state more easily, thus increasing the reaction rate.

**Conclusion:** This statement is **correct**.

### Step 3: Analyze the third statement
**Statement (iii): The catalyst increases the activation energy of the reaction.**

This statement is incorrect. A catalyst is known to lower the activation energy of a reaction, not increase it. By providing an alternative reaction pathway with a lower activation energy, catalysts facilitate faster reactions. Therefore, this statement contradicts the fundamental principle of catalysis.

**Conclusion:** This statement is **incorrect**.

### Final Conclusion:
Based on the analysis, the correct factors responsible for the increase in the rate of a surface-catalyzed reaction are:
- Statement (i) is correct.
- Statement (ii) is correct.
- Statement (iii) is incorrect.

Thus, the answer is that **statements (i) and (ii) are responsible for the increase in the rate of a surface-catalyzed reaction**.

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