Which of the following statements are correct ?

Options

A. Hydrogenation is an exothermic reaction.
B. Heat of hydrogenation is better than heat of combustion for meansuring the stabilities of alkenes.
C. Among the isomeric alkenes, the most stable alkene has the lowest heat `(` more negative value `)` of hydrogenation and the highest heat of combustion and heat of formation `(` less negative value `)`.
D. Among the isomeric alkenes, the most stable alkene has the lowest value of heat of hydrogenation, heat of combustion, and heat of formation `(` more negative value `).`

Explanation

To determine which statements regarding hydrogenation and the properties of alkenes are correct, let's analyze each statement step by step.

### Step-by-Step Solution:

1. **Statement A: Hydrogenation is an exothermic reaction.**
- **Analysis:** In hydrogenation, alkenes react with hydrogen (H₂) in the presence of a catalyst (like platinum) to form alkanes. This reaction releases heat because the less stable pi bond in the alkene is converted into a more stable sigma bond in the alkane. Since the formation of a more stable compound releases energy, this statement is correct.
- **Conclusion:** **Correct**

2. **Statement B: Heat of hydrogenation is better than heat of combustion for measuring the instabilities of the alkene.**
- **Analysis:** The heat of hydrogenation provides a direct measure of the stability of alkenes. More stable alkenes release less heat during hydrogenation, indicating lower instability. In contrast, heat of combustion is typically used to compare the stability of geometrical isomers rather than to assess the stability of alkenes directly. Therefore, this statement is also correct.
- **Conclusion:** **Correct**

3. **Statement C: Among the isomeric alkenes, the most stable alkene has the lowest heat of hydrogenation (more negative value) and the highest heat of combustion (less negative value).**
- **Analysis:** The most stable alkene actually has the **highest** heat of hydrogenation (less negative value) because it releases less heat upon hydrogenation. Conversely, it has the **lowest** heat of combustion (more negative value) because it is more stable and releases less energy when combusted. Therefore, this statement is incorrect.
- **Conclusion:** **Incorrect**

4. **Statement D: Among the isomeric alkenes, the most stable alkene has the lowest value of heat of hydrogenation, heat of combustion, and heat of formation.**
- **Analysis:** This statement is misleading. The most stable alkene has the **lowest** heat of hydrogenation (less negative value), but it does not necessarily have the lowest heat of combustion or heat of formation. The heat of combustion is generally higher for more stable alkenes, and the heat of formation can vary. Therefore, this statement is also incorrect.
- **Conclusion:** **Incorrect**

### Final Conclusions:
- **Correct Statements:** A and B
- **Incorrect Statements:** C and D