Question

In a heterogeneous equilibrium, the concentrations of pure solids and pure liquids are ignored in the equilibrium expression for the reaction because

Options:

-they are not required for the equilibrium to be established.
-their concentrations remain constant and do not affect the expression.
-they do not participate in the reaction.
-they need not be present in the equilibrium mixture.

Answer 1

In a heterogeneous equilibrium, concentrations of pure solids and liquids are not included in the equilibrium expression because they remain constant and do not change during the reaction, ensuring the expression only includes variables that can actually change.

Step-by-step explanation:

In a heterogeneous equilibrium, the concentrations of pure solids and pure liquids are ignored in the equilibrium expression for the reaction because their concentrations remain constant and do not affect the expression. This is because a pure solid or a pure liquid has a fixed concentration that does not change during the course of the reaction, assuming there is sufficient quantity present to reach equilibrium.

Therefore, when writing the equilibrium constant expression for such a system, only the partial pressures of gases or concentrations of solutions are included.

For instance, in the decomposition of mercury (II) oxide, the equilibrium constant expression would not include the solid mercury (II) oxide or the liquid mercury that may be involved in the reaction, but instead would focus on the concentration of gaseous substances, such as the oxygen that is produced.