When the concentration of Mg2+ decreases, how does the equilibrium shift according to Le Chatelier's Principle?

Le Chatelier's Principle states that if a system at equilibrium is subjected to a change in concentration, temperature, or pressure, the system will respond by shifting in the direction that counteracts the change in order to re-establish equilibrium.

In this scenario, when the concentration of Mg2+ decreases, the equilibrium will shift in such a way as to increase the concentration of Mg2+ back toward its original state. This occurs because the system seeks to counter the reduction in Mg2+ concentration.

If the reaction involves the formation or consumption of Mg2+, the decrease in Mg2+ concentration will prompt the equilibrium to shift toward the left, favoring the reactants, thus producing more Mg2+. This is consistent with the principle that the system aims to counterbalance the disturbance caused by the decreased concentration of Mg2+.

Consequently, it can be concluded that the equilibrium shifts to the left when the concentration of Mg2+ decreases, supporting the answer chosen.