How do you calculate the equilibrium constant for a reaction?

The equilibrium constant for a reaction is calculated by dividing the product of concentrations of the products by the reactants.

The equilibrium constant, also known as the reaction quotient, is a measure of the ratio of the concentrations of products to reactants at equilibrium. It is denoted by the symbol K. The equilibrium constant is calculated using the law of mass action which states that the rate of a chemical reaction is directly proportional to the product of the molar concentrations of the reactants.

To calculate the equilibrium constant, you need to know the balanced chemical equation for the reaction and the concentrations of all reactants and products at equilibrium. The general formula for the equilibrium constant is K = [C]^c[D]^d / [A]^a[B]^b, where [A], [B], [C], and [D] represent the molar concentrations of the reactants and products, and a, b, c, and d are their respective coefficients in the balanced chemical equation.

For example, for the reaction aA + bB ⇌ cC + dD, the equilibrium constant K would be calculated as K = ([C]^c [D]^d) / ([A]^a [B]^b). The concentrations are raised to the power of their stoichiometric coefficients in the balanced chemical equation.

It's important to note that only gases and aqueous solutions are included in the equilibrium constant expression. Pure solids and liquids are not included because their concentrations do not change.

The value of the equilibrium constant gives important information about the system at equilibrium. If K is greater than 1, the reaction favours the products at equilibrium. If K is less than 1, the reaction favours the reactants at equilibrium. If K is equal to 1, the amounts of reactants and products are equal at equilibrium.

Remember, the equilibrium constant is temperature dependent. If the temperature changes, the value of K will also change.