The energies of activation for forward and reverse reaction for `A_(2)+B_(2) hArr 2AB` are `180 kJ "mol"^(-1)` and `200 kJ "mol"^(-1)` respectively. The presence of catalyst lowers the activation energy of both (forward and reverse) reactions by `100 kJ "mol"^(-1)`. The enthalpy change of the reaction `(A_(2) + B_(2) rarr 2 AB)` in the presence of catalyst will be (in `kJ "mol"^(-1)`):

Options

A. 380
B. 280
C. 20
D. 120

Answer

C

Explanation

Presence of a catalyst does not change the reaction enthalpy
`Delta_(r)H^(Ɵ)=(E_(a))_(f)-(E_(a))_(r)`
`=(180KJmol^(-1))-(200KJmol^(-1))`
`=-20KJmol^(-1)`