In an exothermic reaction `X rarr Y`, the activation energy is `100 kJ mol^(-1)` of `X`. The enthalphy of the reaction is `-140 kJ mol^(-1)`. The activation energy of the reverse reaction `Y rarr X` is

Options

A. `40 kJ mol^(-1)`
B. `340 kJ mol^(-1)`
C. `240 kJ mol^(-1)`
D. `100 kJ mol^(-1)`

Answer

C

Explanation

For `X rarr Y:(E_(a))_(f) = 100 kJ mol^(-1)`
`Delta H = -140 kJ mol^(-1) =| 140 kJ mol^(-1)|`
Form the figure above `(E_(a))_(b) = (E_(a))_(f) + Delta H`
`= 100 + 140 + 240 = kJmol^(-1)`