2002 AIPMT EquilibriumHeterogeneous Equilibrium and Le Chatelier's Principle Medium Question 93 of 104 in Equilibrium

Reaction $BaO_2(s) \rightleftharpoons BaO(s) + O_2(g)$; $\Delta H$ = +ve. In equilibrium condition, pressure of $O_2$ depends on : -

A Increase mass of $BaO_2$
B Increase mass of BaO
C Increase temp. on Eqm.
D Increase mass of $BaO_2$ and BaO both

The answer is C.

Solution

For this heterogeneous equilibrium, the solids do not appear in the equilibrium expression (their activity is constant): $K_p = p_{O_2}$.
So the equilibrium pressure of $O_2$ equals $K_p$. Adding more $BaO_2$ or BaO does not change it.
$K_p$ changes only with temperature. The forward reaction is endothermic ($\Delta H$ positive), so by Le Chatelier's principle an increase in temperature shifts the equilibrium forward and increases $p_{O_2}$.
So the pressure of $O_2$ depends on increasing the temperature at equilibrium.

Concept Kp depends only on temperature

Equilibrium in past papers

104 questions from this chapter have appeared across 27 exam years.