# The energies of activation for forward and reverse reactions for $\dpi{100} A_{2}+B_{2}\rightleftharpoons 2AB\; are\; 180\; kJ\; mol^{-1}\; and\; 200\; kJ\; mol^{-1}$ respectively. The presence of a catalyst lowers the activation energy of both (forward and reverse) reactions by $\dpi{100} 100\; kJ\; mol^{-1}$ . The enthalpy change of the reaction $\dpi{100} (A_{2}+B_{2}\rightarrow 2AB)$in the presence of a catalyst will be  $\dpi{100} (in\; kJ\; mol^{-1})$ Option 1) 20 Option 2) 300 Option 3) 120 Option 4) 280

D Divya Saini

As we learnt in

Catalyst -

A catalyst is a surface that increases the rate of a chemical reaction without itself being used up. It remains unchanged chemically providing an alternate path for the reaction at an accelerated rate by lowering the activation energy.

- wherein

Enthalpy change of reaction do not change by adding catalyst.

$\bigtriangleup H = 200-180 = 20 KJmol^{-1}$

Option 1)

20

This option is correct

Option 2)

300

This option is correct

Option 3)

120

This option is incorrect

Option 4)

280

This option is incorrect

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