Question

When $I_2$ dissociated to its form the following reaction occurs:
$I_{2\left(g\right)}\rightleftharpoons 2I_{\left(g\right)};△H^0=+150$kJ.
The reaction is favoured at ?

• A. low temperature
• B. high temperature
• C. no change with temperature
• D. high pressure.

Answer 1

Answer: (B)

high temperature

$I_2\left(g\right)\rightleftharpoons 2I\left(g\right);\Delta H^o=+150KJ$
From Gibbs free energy change equation,
$\Delta G=\Delta H-T\Delta S$
If $\Delta H>0$ then $\Delta G<0$ when T is high.

Since here the heat is consumed by the reaction, it is an endothermic reaction, i.e reactants require heat or energy to overcome the forces of attraction between molecules and to separate them from one another (the activation energy) than the energy gained when new bonds are formed. Thus high temperatures are required for this.
Hence, option B is correct.