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

Options

A. 120
B. 280
C. 20
D. 300

Answer

C

Explanation

(C ) Enthalpy change of a reaction is not effected by the presence of catalyst because it lowers the activation energy of the forward and the reverse reaction of the same exten .
`DeltaH = E_(a) (f) - E_(a ) ( r)`
=180 -200
`=- 20 ` kJ `"mol"^(-1)`
None of the option is correct butg option (C ) may be treated as correct in term of magnitude .