A: The reaction `2NO(g) +O_2(g) hArr 2NO_2(g)` is
favoured in the forward direction with increase of pressure.
R : The above reaction is exothermic .

Options

A. If both Assertion & Reason are true and the reason in the corret explanation of the assertion, then mark
B. If both assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark
C. If Assertion is true statement but Reason is false then mark
D. If both Assertion and Reason are false statements , then mark

Answer

To solve the question, we need to analyze both the assertion (A) and the reason (R) provided:

**Assertion (A):** The reaction \(2NO(g) + O_2(g) \rightleftharpoons 2NO_2(g)\) is favored in the forward direction with an increase of pressure.

**Reason (R):** The above reaction is exothermic.

### Step-by-Step Solution:

1. **Understanding the Reaction:**
The reaction involves the conversion of nitrogen monoxide (NO) and oxygen (O2) into nitrogen dioxide (NO2).

2. **Analyzing the Effect of Pressure:**
According to Le Chatelier's principle, if the pressure of a system at equilibrium is increased, the equilibrium will shift in the direction that produces fewer moles of gas.

- In this reaction:
- Reactants: \(2 \, \text{NO} + 1 \, \text{O}_2\) = 3 moles of gas
- Products: \(2 \, \text{NO}_2\) = 2 moles of gas
- Since there are 3 moles of gas on the reactant side and only 2 moles on the product side, increasing the pressure will shift the equilibrium to the right (forward direction) to produce more NO2.

3. **Determining the Truth of the Assertion:**
Since the equilibrium shifts towards the side with fewer moles of gas when pressure is increased, the assertion is **true**.

4. **Analyzing the Exothermic Nature of the Reaction:**
The reason states that the reaction is exothermic. An exothermic reaction releases heat. While this is true, it does not directly relate to the effect of pressure on the equilibrium position in this specific case.

5. **Determining the Truth of the Reason:**
The reason is also **true**, but it does not provide a correct explanation for the assertion about pressure. The assertion is about the shift in equilibrium due to pressure, while the reason discusses the heat change.

6. **Conclusion:**
Both the assertion and reason are true, but the reason does not explain the assertion. Therefore, the correct option is **B**: Both assertion and reason are true, but the reason is not the correct explanation of the assertion.

### Final Answer:
**B**: Both assertion and reason are true, but the reason is not the correct explanation of the assertion.

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