Which is a characteristic of a catalyst ?

Options

A. Alters the equilibrium in a reaction
B. Is always in the same phase as the reactants
C. Participates in the reaction and provides easier pathway for the same
D. Does not participate in the reaction

Answer

To determine the characteristic of a catalyst, we can analyze the options provided and understand the fundamental properties of catalysts. Here’s a step-by-step breakdown of the solution:

### Step 1: Understand the Definition of a Catalyst
A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. It achieves this by providing an alternative reaction pathway with a lower activation energy.

**Hint:** Remember that a catalyst is not consumed in the reaction; it is regenerated at the end.

### Step 2: Evaluate the Options
1. **Option 1: Alters the equilibrium in a reaction**
- This statement is incorrect. A catalyst does not change the position of equilibrium; it only helps the system reach equilibrium faster.

**Hint:** Recall that catalysts affect reaction rates, not equilibrium positions.

2. **Option 2: Always in the same phase as that of the reactants**
- This statement is also incorrect. Catalysts can be in the same phase (homogeneous) or a different phase (heterogeneous) than the reactants.

**Hint:** Consider examples where solid catalysts are used with gaseous or liquid reactants.

3. **Option 3: Participates in the reaction and provides an easier pathway**
- This statement is correct. Catalysts do participate in the reaction mechanism and lower the activation energy, making the reaction proceed more easily.

**Hint:** Think about how catalysts lower activation energy and speed up reactions.

4. **Option 4: Does not participate in the reaction**
- This statement is incorrect. Catalysts do participate in the reaction, although they are not consumed.

**Hint:** Remember that participation means they are involved in the mechanism but are regenerated.

### Step 3: Conclusion
Based on the evaluation of the options, the characteristic of a catalyst is best described by **Option 3: It participates in the reaction and provides an easier pathway for the same**.

**Final Answer:** The characteristic of a catalyst is that it participates in the reaction and provides an easier pathway for the same.