In a spontaneous reaction, the free energy of a system -

Options

A. Decreases
B. Increases
C. Becomes equal to zero
D. Remains unchanged

Answer

To answer the question, "In a spontaneous reaction, the free energy of a system -", we need to analyze the behavior of Gibbs free energy (ΔG) during spontaneous reactions.

### Step-by-Step Solution:

1. **Understanding Spontaneous Reactions**:
- A spontaneous reaction is one that occurs without needing to be driven by an external force. It proceeds naturally under given conditions.

2. **Gibbs Free Energy (ΔG)**:
- Gibbs free energy is a thermodynamic potential that can predict the direction of chemical reactions. It is represented as ΔG.

3. **Criteria for Spontaneity**:
- For a reaction to be spontaneous, the change in Gibbs free energy (ΔG) must be negative. This indicates that the free energy of the system decreases as the reaction proceeds.

4. **Exergonic Reactions**:
- Spontaneous reactions are often referred to as exergonic reactions. In these reactions, energy is released, leading to a decrease in free energy.

5. **Equilibrium and Non-Spontaneous Reactions**:
- If ΔG is zero, the system is at equilibrium, meaning there is no net change in the system. If ΔG is positive, the reaction is non-spontaneous and requires energy input to proceed.

6. **Conclusion**:
- Therefore, in a spontaneous reaction, the free energy of the system decreases. The correct answer is that the free energy decreases.

### Final Answer:
In a spontaneous reaction, the free energy of a system decreases.

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