Looking for classes? Ksquare Career Institute, Bengaluru →
Bond enthalpy
Concepts tested here
- Bond dissociation energy
All Questions
2011 AIPMT-PRE 1 question
-
Enthalpy change for the reaction, $4H(g) \rightarrow 2H_2(g)$ is −869.6 kJ. The dissociation energy of H–H bond is$4H(g) \rightarrow 2H_2(g)$; $\Delta H = -869.6$ kJ. In this reaction 2 moles of H–H bonds are formed.
Energy released in forming 1 mole of H–H bonds = $\frac{869.6}{2} = 434.8$ kJ
Bond dissociation is the reverse process: $H_2(g) \rightarrow 2H(g)$, which absorbs the same amount of energy.
Bond dissociation energy is therefore positive (endothermic).
Dissociation energy of the H–H bond = +434.8 kJ