Question

In a equilibrium reaction $H_2\left(g\right)+I_2\left(g\right)\rightleftharpoons 2HI\left(g\right)$
$\Delta H=-3000calories$, which factor favours dissociation of HI :-

• A. Low temp.
• B. High Pressure
• C. High temp.
• D. Low pressure.

Answer 1

Answer: (C)

High temp.

In a equilibrium reaction $H_2\left(g\right)+I_2\left(g\right)\rightleftharpoons 2HI\left(g\right)$
$\Delta H=-3000calories$, High temp. favours dissociation of $HI$ . negative value of the enthalpy change indicates that the reverse reaction (dissociation of $HI$) is endothermic in nature.
At high temperature, the equilibrium will shift in the reverse direction so that more and more heat is absorbed during the reaction which nullifies the effect of high temperature.