Which of the following values of heat of formation does indicate that the product is least stable ?
- 94 kcal
- 231.5 kcal
+64.8 kcal.
+21.4 kcal

Options

A. - 94 kcal
B. - 231.5 kcal
C. +21.4 kcal
D. +64.8 kcal.

Explanation

To determine which value of heat of formation indicates that the product is least stable, we need to understand the relationship between heat of formation and stability.

### Step-by-Step Solution:

1. **Understanding Heat of Formation**: The heat of formation (ΔH_f) is the change in enthalpy when one mole of a compound is formed from its elements in their standard states. It can be either negative (exothermic reaction) or positive (endothermic reaction).

2. **Stability and Heat of Formation**:
- Compounds with a **negative heat of formation** release energy when formed, indicating they are more stable.
- Compounds with a **positive heat of formation** absorb energy when formed, indicating they are less stable.

3. **Analyzing the Given Values**:
- **-94 kcal**: This indicates an exothermic reaction, suggesting stability.
- **-231.5 kcal**: This also indicates an exothermic reaction, suggesting even greater stability than -94 kcal.
- **+64.8 kcal**: This indicates an endothermic reaction, suggesting that the product is less stable.
- **+21.4 kcal**: This also indicates an endothermic reaction, but less so than +64.8 kcal.

4. **Conclusion**: Among the given options, the highest positive value of heat of formation is **+64.8 kcal**, which indicates that this product is the least stable because it requires the most energy to form.

### Final Answer:
The product with a heat of formation of **+64.8 kcal** indicates that it is the least stable.

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