Question

For an endothermic reaction where $\Delta H$ represents the enthalpy of the reaction in $kJmo{l}^{-1}$, the minimum value for the energy of activation will be:

• A. less than $\Delta H$
• B. zero
• C. more than $\Delta H$
• D. equal to $\Delta H$

Answer 1

The correct option is C more than $\Delta H$

Activation energy: $E_a$ is the energy that must be possessed by the molecules in excess to the average energy at a given temperature to enter a chemical reaction.

Relation between activation energy and enthalpy of a reversible reaction:

If the reaction is endothermic in forward direction, then $E_{a\left(backward\right)}=E_{a\left(forward\right)}+\Delta H$

If the reaction is exothermic in forward direction then $E_{a\left(backward\right)}=E_{a\left(forward\right)}+\Delta H$

For an endothermic reaction, where $\Delta H$ represents the enthalpy of

the reaction in $kJmo{l}^{-1}$, the minimum value for the energy of activation will be slightly more than $\Delta H$.