In calculating K, which value equals zero/one for solids and solvents?

In the context of calculating the equilibrium constant (K) for a chemical reaction, the value for solids and solvents is defined as one. This approach is based on the principle that the activities of pure solids and liquids are taken to be equal to one in order to simplify the expression for K.

This simplification occurs because the concentration of pure solids and the effective concentration of a pure solvent do not change during a reaction; their activity is constant. Therefore, when forming the equilibrium expression, solids and solvents do not appear with their concentrations raised to a power because their contribution to the reaction's quotient is effectively neutral.

Consequently, for any equilibrium calculation, while the concentrations of gaseous reactants and products and the concentrations of dissolved substances in solution will be included in the K expression, the values for solids and solvents are treated as one, simplifying the overall equation and allowing for a more straightforward calculation of equilibrium concentrations.