The energy change accompanying the equilibrium reaction `A hArr B` is `-33.0 kJ mol^(-1)`.

Assuming that pre-exponential factor is same for forward and backward reaction answer the following:
The energy of activation for forward and backward reactions (`E_(f)` and `E_(b)`) at `300 K`. Given that `E_(f)` and `E_(b)` are in the ratio `20 : 31`,

Options

A. `69, 93`
B. `60, 93`
C. `93, 60`
D. `90, 60`

Answer

B

Explanation

`(E_(f))/(E_(b)) = (20)/(31)` (given). Also `E_(f) = E_(b) = -33` (given) …(i)
Substituting `E_(b) = (31)/(20) E_(f)`, in Eq. (i) we get
`E_(f) - (31)/(20) E_(f) = -33`
or `(-11)/(20)E_(f) = -33` or `E_(f) = (33 xx 20)/(11) = 60 kJ mol^(-1)`
`E_(b) = E_(f) + 33 = 60 + 33 = 93 kJ mol^(-1)`