Magnesium carbonate dissociates to magnesium oxide and carbon dioxide at elevated temperatures. MgCO3 (s) MgO (s) + CO2 (g) A reaction vessel contains these compounds in equilibrium at 300°C. What will happen if the volume of the container is reduced by 25% at 300°C? Multiple Choice The partial pressure of carbon dioxide present at equilibrium will increase. The partial pressure of carbon dioxide present at equilibrium will decrease. The partial pressure of carbon dioxide at equilibrium will be unchanged. The equilibrium constant will have to decrease to compensate for the decrease in volume. More information is needed in order to make a valid judgment.

The partial pressure of carbon dioxide present at equilibrium will decrease.

Explanation:

Let's consider the following reaction.

MgCO₃ (s) ⇄ MgO (s) + CO₂ (g)

What will happen if the volume of the container is reduced by 25% at 300°C?

To answer this question we need to consider Le Chatelier's Principle: if a system at equilibrium suffers a perturbation, it will shift its equilibrium position to counteract such perturbation.

If the volume of the container is reduced, according to Boyle's Law, the pressure of the gases will increase. Thus, the system will try to decrease the pressure by favoring the reverse reaction because there are less gaseous moles in the reactants than in the products. As a consequence, the partial pressure of carbon dioxide present at equilibrium will decrease.