Equilibrium Constants in Chemical Reactions

The equilibrium constant, Kc, for a reversible reaction is the ratio of the product concentrations to the reactant concentrations, each raised to the power of their stoichiometric coefficient. For the reaction aA + bB <=> cC + dD, the equilibrium constant expression is Kc = [C]^c * [D]^d / [A]^a * [B]^b. The square brackets indicate molar concentrations.

The equilibrium constant expression for the reaction 2NO(g) + Cl2(g) <=> 2NOCl(g) is Kc = [NOCl]^2 / [NO]^2 * [Cl2]. The product NOCl is in the numerator, raised to the power of 2, and the reactants NO and Cl2 are in the denominator, each raised to the power of their stoichiometric coefficient. This expression quantifies the relative amounts of products and reactants at equilibrium.

The equilibrium constant expression for the reaction Ag+(aq) + 2NH3(aq) <=> Ag(NH3)2+(aq) is Kc = [Ag(NH3)2+] / [Ag+] * [NH3]^2. The product Ag(NH3)2+ is in the numerator, and the reactants Ag+ and NH3 are in the denominator, raised to the power of their stoichiometric coefficients.

The equilibrium constant expression for the reaction H2(g) + I2(g) <=> 2HI(g) is Kc = [HI]^2 / [H2] * [I2]. The product HI is in the numerator, squared, and the reactants H2 and I2 are in the denominator, each raised to the power of 1.

The equilibrium constant expression for the reaction Cd2+(aq) + 4Br-(aq) <=> CdBr42-(aq) is Kc = [CdBr42-] / [Cd2+] * [Br-]^4. The product CdBr42- is in the numerator. Reactants Cd2+ and Br- are in the denominator, Cd2+ raised to the power of 1 and Br- raised to the power of 4.

A constant value that describes the ratio of product concentrations to reactant concentrations when a reaction has reached equilibrium. It reflects the relative amounts of reactants and products at equilibrium.

The state where the rate of the forward reaction equals the rate of the reverse reaction, and the concentrations of reactants and products remain constant.

The ratio of the concentrations of products to the concentrations of reactants, each raised to the power of their stoichiometric coefficient, in a balanced chemical equation.

A change in the initial concentrations of reactants or products does not change the value of the Equilibrium Constant (Kc).

The initial concentration of reactants or products does not affect the final equilibrium mixture. Equilibrium can be achieved starting with either reactants or products.

The value of Kc for a reaction is constant at a given temperature.

A change in the concentration of one or more reactants or products will shift the reaction to re-establish a new equilibrium.

A change in pressure will favor the side of the reaction with fewer gas moles.

The equilibrium constant, Kp, for a reaction is unaffected by changes in the stoichiometric coefficients of the balanced reaction.

The equilibrium constant for a net reaction is the product of the equilibrium constants for the individual reactions that add up to give the net reaction.

If you reverse a reaction, the equilibrium constant of the reverse reaction is the inverse (reciprocal) of the equilibrium constant of the forward reaction.

The equilibrium constant, Kc, for a reaction is the ratio of the product concentrations to the reactant concentrations, each raised to the power of their stoichiometric coefficient. For the reaction aA + bB <=> cC + dD, the equilibrium constant expression is Kc = [C]^c * [D]^d / [A]^a * [B]^b. The square brackets indicate molar concentrations.

The equilibrium constant, Kp, for a reaction is the ratio of the partial pressures of the products to the partial pressures of the reactants, each raised to the power of their stoichiometric coefficient. For the reaction aA + bB <=> cC + dD, the equilibrium constant expression is Kp = (P_C)^c * (P_D)^d / (P_A)^a * (P_B)^b.

The activity of a pure solid or liquid is always 1.

The equilibrium constant expression for a heterogeneous reaction does not include the concentrations of pure solids or liquids.

Kp is the equilibrium constant expressed in terms of partial pressures.

The equilibrium constant for the reaction CaCO3(s) ⇌ CaO(s) + CO2(g) is Kc = [CO2] and Kp = PCO2. This means at a given temperature, the equilibrium pressure of CO2 is constant regardless of the amounts of CaO and CaCO3 present.

The equilibrium constant expression for the reaction CO2(g) + H2(g) ⇌ CO(g) + H2O(l) is Kc = [CO] / [CO2][H2].

The equilibrium constant expression for the reaction SnO2(s) + 2 CO(g) ⇌ Sn(s) + 2 CO2(g) is Kc = [CO2]^2 / [CO]^2.

If the temperature of a system at equilibrium is increased, the reaction will shift to favor the endothermic direction, consuming added heat. If the temperature is decreased, the reaction will shift to favor the exothermic direction, releasing heat.

The side of the equilibrium with fewer gas moles will be favored by an increase in pressure.

Adding a reactant will shift the equilibrium to favor the product side, while removing a reactant will shift it to favor the reactant side. The opposite is true for products.

Adding or removing heat to a reaction at equilibrium will shift the equilibrium to favor the endothermic or exothermic direction, respectively.

The equilibrium constant, Kc, is unaffected by changes in the initial concentrations of reactants or products.

Adding a reactant or product to a system at equilibrium will cause the system to shift to consume some of the added substance. Removing a substance will cause the system to produce more of that substance.

Reducing the volume of a gaseous equilibrium mixture at constant temperature will shift the system towards the side with fewer moles of gas.

Equilibrium can be reached from either direction, starting with reactants or products. The final equilibrium mixture will be the same.