Question

For a reaction $A \rightarrow B$, the average energies of $A$ and $B$ are $30$ and $60 \,kcal / mol$ respectively. Energy of the activation for the backward reaction is $93 \, kcal / mol$. The energy of activation for the forward reaction is

• A. 30 kcal / mol
• B. 123 kcal / mol
• C. 153 kcal / mol
• D. 90 kcal / mol

Answer 1

Answer: (B)

Activation energy is the energy that must be provided to compound to result in a chemical reaction.
Given, for the reaction $A \rightarrow B$.
$E_{b}$ or average energy of $(A)=30 \,kcal / mol$
Average energy of $(B)=60 \, kcal / mol$
and energy of activation for backward reaction
$=93\, kcal / mol \left( H _{f}\right)$
Also, $\because H_{f}=E_{a}(f)-E_{b}$
$\therefore E_{a}(f)=H_{f}+E_{b}=93+30=123 \,kcal / mol$