The equilibrium constant K for the reaction `2HI(g) hArr H_(2)(g)+I_(2)(g)` at room temperature is `2.85` and that at `698 K` is `1.4 xx10^(-2)`. This implies

Options

A. `HI` is exothermic compound
B. `HI` is very stable at room temperature
C. `HI` is relatively less stable than `H_(2)` and `I_(2)` at room temperature
D. `HI` is resonance stablised

Explanation

To solve the problem, we need to analyze the given equilibrium constants (K) at two different temperatures and determine the implications regarding the nature of the reaction.

### Step-by-Step Solution:

1. **Identify the Reaction**:
The reaction given is:
\[ 2 \text{HI}(g) \rightleftharpoons \text{H}_2(g) + \text{I}_2(g) \]

2. **Equilibrium Constants at Different Temperatures**:
- At room temperature (approximately 298 K), the equilibrium constant \( K_c \) is 2.85.
- At 698 K, the equilibrium constant \( K_c \) is \( 1.4 \times 10^{-2} \).

3. **Analyze the Change in K with Temperature**:
- We observe that as the temperature increases from 298 K to 698 K, the value of \( K_c \) decreases from 2.85 to \( 1.4 \times 10^{-2} \).
- A decrease in the equilibrium constant with an increase in temperature suggests that the reaction favors the reactants at higher temperatures.

4. **Determine the Nature of the Reaction**:
- According to Le Chatelier's principle, if the equilibrium constant decreases with an increase in temperature, the reaction is exothermic in the forward direction. This means that heat is released during the formation of products (H2 and I2) from reactants (HI).
- Therefore, the reaction can be classified as exothermic.

5. **Conclusion about Stability**:
- Since the reaction is exothermic, it implies that the reactants (HI) have higher energy compared to the products (H2 and I2).
- This indicates that HI is less stable than H2 and I2 at room temperature, as higher energy correlates with greater instability.

6. **Final Statement**:
- The correct implication from the given data is that HI is relatively less stable than H2 and I2 at room temperature.