• # question_answer The reaction  $\operatorname{X}\to \operatorname{Y}$ is an exothermic reaction. Activation energy of the reaction for X into $\operatorname{Y}$ is 150 $150\operatorname{K}\operatorname{J}{{\operatorname{mol}}^{-1}}$. Enthalpy of reaction is $135\operatorname{K}\operatorname{J}{{\operatorname{mol}}^{-1}}$. The activation energy for the reverse reaction, $\operatorname{Y}\to \operatorname{X}$ will be:     JEE Main  Online Paper (Held On 22 April 2013) A)  $280\operatorname{kJ}{{\operatorname{mol}}^{-1}}$                            B)  $285\operatorname{kJ}{{\operatorname{mol}}^{-1}}$            C)  $270\operatorname{kJ}{{\operatorname{mol}}^{-1}}$                            D)  $15\operatorname{kJ}{{\operatorname{mol}}^{-1}}$

$X\xrightarrow{{}}Y;\Delta H=-135\,kJ/mol,$ ${{E}_{a}}=150\,kJ/mol$ For an exothermic reaction ${{E}_{a(F.R.)}}=\Delta H+E_{a(B.R)}^{'}$ $150=-135+E_{a(B.R.)}^{'}$ $E_{a(B.R)\,}^{'}=285\,kJ/mol$