Question

For a reaction $A \to B; \Delta H = 20 \, kJ \, mol^{-1}$ the activation energy of the forward reaction is $85 \,kJ/mol$. The activation energy of the backward reaction will be

• A. 105 kJ/mol
• B. 65 kJ/mol
• C. 45 kJ/mol
• D. 75 kJ/mol

Answer 1

Answer: (B)

Energy of activation for forward reaction $\left( E _{ a }\right)=85\, kJ / mol$ and
$\Delta H =20\, kJ / mol$
$\therefore $ Energy of activation for backward reaction
$E _{ b }= E _{ a }-\Delta H =85-20=65 \,kJ\,mol ^{-1}$