Each question contains STATEMENT-1 (Assertion) and STATEMENT-2( Reason).
Examine the statements carefully and mark the correct answer according to the instruction given below:
STATEMENT-1: For the reaction at certain temperature
`A(g)+B(g) iff C(g)`
there will be no effect by addition of inert gas at constant volume.
STATEMENT-2: Molar concentration of all gases remains constant.

Options

A. If both the statements are TRUE and STATEMENT-2 is the correct explanation of STATEMENT-1
B. If both the statement are TRUE but STATEMENT-2 is NOT the correct explanation of STATEMENT-1
C. If STATEMENT-1 is TRUE and STATEMENT-2 is FALSE
D. If STATEMENT-1 is FALSE and STATEMENT-2 is TRUE

Answer

To solve the question, we need to analyze both statements provided:

**STATEMENT-1**: For the reaction at a certain temperature, \( A(g) + B(g) \iff C(g) \), there will be no effect by the addition of an inert gas at constant volume.

**STATEMENT-2**: Molar concentration of all gases remains constant.

### Step-by-Step Solution:

1. **Understanding the Reaction**: The reaction given is \( A(g) + B(g) \iff C(g) \). This is a dynamic equilibrium where the forward and reverse reactions occur simultaneously.

2. **Effect of Inert Gas Addition**: When an inert gas (like helium or argon) is added to the system at constant volume, it does not react with the gases involved in the equilibrium. According to Le Chatelier's principle, the addition of an inert gas at constant volume does not change the partial pressures of the reacting gases.

3. **Concentration Calculation**: The concentration of a gas is defined as the number of moles of gas divided by the volume of the container. If we denote:
- \( n_1 \) = moles of \( A \)
- \( n_2 \) = moles of \( B \)
- \( n_3 \) = moles of \( C \)
- \( V \) = volume of the container

The concentrations are:
- Concentration of \( A \) = \( \frac{n_1}{V} \)
- Concentration of \( B \) = \( \frac{n_2}{V} \)
- Concentration of \( C \) = \( \frac{n_3}{V} \)

4. **Impact of Inert Gas**: When an inert gas is added at constant volume, the total pressure increases, but the partial pressures (and thus the concentrations) of \( A \), \( B \), and \( C \) remain unchanged because the number of moles of the reacting gases does not change.

5. **Conclusion on Statements**:
- **STATEMENT-1** is true: The addition of an inert gas at constant volume does not affect the equilibrium.
- **STATEMENT-2** is also true: The molar concentrations of all gases remain constant when an inert gas is added at constant volume.

6. **Correct Explanation**: Since both statements are true and STATEMENT-2 correctly explains STATEMENT-1, the answer is that both statements are true, and STATEMENT-2 is the correct explanation for STATEMENT-1.

### Final Answer:
Both statements are true, and STATEMENT-2 is the correct explanation for STATEMENT-1.

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