Question

The reaction $X \rightarrow Y$ is an exothermic reaction. Activation energy of the reaction for $X$ into $Y$ is $150\, kJ mol^{-1}$. Enthalpy of reaction is $135\, kJ\, mol^{-1}$. The activation energy for the reverse reaction, $Y \rightarrow X$ will be:

• A. $280\, kJ\,mol^{-1}$
• B. $285\, kJ\,mol^{-1}$
• C. $270\, kJ\,mol^{-1}$
• D. $15\, kJ\,mol^{-1}$

Answer 1

Answer: (B)

$X \rightarrow Y; \Delta H=-135\,kJ/mol,$
$E_{a}=150\,kJ/mol$
For an exothermic reaction
$E_{a\left(F.R.\right)}=\Delta H+E'_{a\left(B.R.\right)}$
$150=-135+E'_{a\left(B.R.\right)}$
$E'_{a\left(B.R.\right)}=258\,kJ/mol,$