Detailed Explanation:

Question:
A catalyst:

• (1) Reduces the free energy change of the reaction

• (2) Increases the free energy change of the reaction

• (3) Reduces the activation energy of the reaction

• (4) Reduces the heat of reaction

Correct Answer:

(3) Reduces the activation energy of the reaction

Explanation:

A catalyst is a substance that accelerates the rate of a chemical reaction without being consumed in the process. While catalysts play an essential role in many biological and industrial processes, their effect on the reaction is often misunderstood. To clarify the role of a catalyst, let’s break down the concepts involved:

Catalyst and Reaction Mechanisms:

1. Activation Energy:

   • Activation energy is the energy required to initiate a chemical reaction. It represents the energy barrier that must be overcome for reactants to be converted into products.

   • A catalyst works by providing an alternative reaction pathway with a lower activation energy. This means that less energy is needed for the reaction to occur, which speeds up the reaction rate.

   • Importantly, the catalyst does not affect the overall free energy change of the reaction. It only influences how quickly the equilibrium is reached by reducing the energy barrier to reaction initiation.

2. Free Energy Change:

   • The free energy change (ΔG) of a reaction represents the difference in energy between the reactants and the products. A catalyst does not change the free energy change of the reaction, meaning it does not affect whether the reaction is exothermic (releases energy) or endothermic (absorbs energy). The catalyst only helps the reaction reach equilibrium faster.

3. Heat of Reaction:

   • The heat of reaction refers to the amount of heat released or absorbed during a reaction. Like the free energy change, a catalyst does not affect the heat released or absorbed by the reaction. Its main role is in speeding up the reaction rate by lowering the activation energy.

Conclusion:

The primary function of a catalyst is to reduce the activation energy of a chemical reaction, which allows the reaction to proceed faster without being consumed in the process. It does not change the free energy or the heat of reaction; it only makes it easier for the reaction to occur by lowering the energy barrier.

Understanding the role of a catalyst is crucial in fields like chemical engineering, pharmacology, and biotechnology, where catalysts are used to increase the efficiency of reactions, save energy, and optimize manufacturing processes.