Dynamic equilibrium, the reaction quotient and equilibrium calculations

Learning objectives

Explain dynamic equilibrium as equal forward and reverse reaction rates with constant concentrations, and represent it with a particulate diagram or a concentration–time graph

Write the expression for K in terms of concentrations or partial pressures, omitting pure solids and liquids, and explain what a very large or very small K value says about the extent of reaction

Relate the equilibrium constants of a reversed, scaled or combined reaction to the original, and convert between Kc and Kp

Calculate equilibrium concentrations or partial pressures using an ICE table, and justify the use of a simplifying approximation when K is small compared with the initial concentration

Compare the reaction quotient Q with K to predict the direction in which a system not at equilibrium will shift, and justify the prediction