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Enthalpy change for the reaction, 4H(g) -> 2H2(g) is -869.6 kJ. The dissociation energy of H-H bond is:

1. -434.8 kJ
2. -869.6 kJ
3. +434.8 kJ
4. +217.4 kJ

Correct answer: +434.8 kJ

Solution

The enthalpy change for the reaction represents the energy released when 2 moles of H2 are formed from 4 moles of H atoms. Since 1 mole of H2 involves the formation of one H-H bond, the dissociation energy of the H-H bond is the positive value of half the given enthalpy change, i.e., +434.8 kJ.

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