Chemistry 2007 JAMB Past Questions - Question 18: C2H4(g) + H2(g) ↔ C2H6(g) ΔH = -137kJ mol. The reaction represented above is

Correct Answer

A

Explanation

The reaction represented above is an **exothermic** **hydrogenation** reaction.

Here's a breakdown of the key points:

- **Exothermic:** The reaction releases heat, indicated by the negative ΔH value of -137 kJ/mol. This means the products have lower energy than the reactants, and energy is released to the surroundings as heat.
- **Hydrogenation:** Hydrogen (H₂) is added to the reactant molecule (C₂H₄), resulting in the formation of a more saturated product (C₂H₆). In this case, a double bond in the reactant is converted into a single bond, increasing the number of hydrogen atoms bonded to the carbon atoms.

Overall, the reaction describes the addition of hydrogen to ethylene (C₂H₄) to form ethane (C₂H₆), releasing heat in the process.