A: A non- spontaneous process becomes spontaneous when coupled with a suitable spontaneous reaction.
R: The overall free energy of coupled spontaneous reaction is negative.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion , then mark (1)
B. If both Assertion & Reason are true and the reason is not the correct explanation of the assertion, then mark (2)
C. If Assertion is true statement but Reason is false, then mark (3)
D. If both Assertion is true statement but Reason is false, then mark (3)

Answer

To determine the validity of the assertion and reason provided in the question, we can analyze them step by step.

### Step 1: Understanding the Assertion
The assertion states that "A non-spontaneous process becomes spontaneous when coupled with a suitable spontaneous reaction."

1. **Definition of Non-spontaneous and Spontaneous Processes**:
- A spontaneous process is one that occurs naturally under given conditions and has a negative change in Gibbs free energy (ΔG < 0).
- A non-spontaneous process requires an input of energy to occur and has a positive change in Gibbs free energy (ΔG > 0).

2. **Coupling Reactions**:
- When a non-spontaneous reaction is coupled with a spontaneous reaction, the overall free energy change can become negative, making the combined process spontaneous.

### Step 2: Example to Illustrate the Assertion
Let's consider the decomposition of calcium carbonate (CaCO3) as a non-spontaneous reaction:
- The reaction is:
\[ \text{CaCO}_3 (s) \rightarrow \text{CaO} (s) + \text{CO}_2 (g) \]
- The ΔG for this reaction is positive (130.40 kJ/mol), indicating it is non-spontaneous.

Now, consider a spontaneous reaction involving carbon:
- The reaction is:
\[ \text{C (s)} + \text{O}_2 (g) \rightarrow \text{CO}_2 (g) \]
- The ΔG for this reaction is negative (-394.35 kJ/mol), indicating it is spontaneous.

### Step 3: Coupling the Reactions
When we couple these two reactions:
\[ \text{CaCO}_3 (s) + \text{C (s)} + \text{O}_2 (g) \rightarrow \text{CaO} (s) + 2 \text{CO}_2 (g) \]
- The overall ΔG for the coupled reaction is calculated as:
\[ \Delta G = \Delta G_{\text{CaCO}_3} + \Delta G_{\text{C + O}_2} \]
- Substituting the values:
\[ \Delta G = 130.40 \text{ kJ/mol} - 394.35 \text{ kJ/mol} = -263.96 \text{ kJ/mol} \]
- Since the overall ΔG is negative, the coupled reaction is spontaneous.

### Step 4: Understanding the Reason
The reason states that "The overall free energy of coupled spontaneous reaction is negative."

1. **Explanation of the Reason**:
- This statement is true because the coupling of a non-spontaneous reaction with a sufficiently spontaneous reaction results in an overall negative ΔG, which indicates that the overall process is spontaneous.

### Conclusion
Both the assertion and reason are true, and the reason provides a correct explanation for the assertion.

### Final Answer
- Both the assertion (A) and reason (R) are true, and R explains A. Therefore, the correct option is **Option 1**.