Chemistry (Chang), 9th EditionChapter 14: Chemical EquilibriumChapter Summary1. Dynamic equilibria between phases are called physical equilibria. Chemical equilibrium
is a reversible process in which the rates of the forward and reverse reactions are
equal and the concentrations of reactants and products do not change with time.
 the concentrations of reactants and products at equilibrium (in moles per liter) are related by the equilibrium constant expression [Equation (14.2)]. 3. The equilibrium constant for gases, KP, expresses the relationship of the equilibrium partial pressures (in atm) of reactants and products. 4. A chemical equilibrium process in which all reactants and products are in the same phase is homogeneous. If the reactants and products are not all in the same phase, the equilibrium is heterogeneous. The concentrations of pure solids, pure liquids, and solvents are constant and do not appear in the equilibrium constant expression of a reaction. 5. If a reaction can be expressed as the sum of two or more reactions, the equilibrium constant for the overall reaction is given by the product of the equilibrium constants of the individual reactions. 6. The value of K depends on how the chemical equation is balanced, and the equilibrium constant for the reverse of a particular reaction is the reciprocal of the equilibrium constant of that reaction. 7. The equilibrium constant is the ratio of the rate constant for the forward reaction to that for the reverse reaction. 8. The reaction quotient Q has the same form as the equilibrium constant, but it applies to a reaction that may not be at equilibrium. If Q > K, the reaction will proceed from right to left to achieve equilibrium. If Q < K, the reaction will proceed from left to right to achieve equilibrium. 9. Le Châtelier’s principle states that if an external stress is applied to a system at chemical equilibrium, the system will adjust to partially offset the stress. 10. Only a change in temperature changes the value of the equilibrium constant for a particular reaction. Changes in concentration, pressure, or volume may change the equilibrium concentrations of reactants and products. The addition of a catalyst hastens the attainment of equilibrium but does not affect the equilibrium concentrations of reactants and products. |  |
