EQUILIBRIUM CONSTANTS Chapter 18.2

OBJECTIVE I will be able to calculate the equilibrium constant of a reaction

EQUILIBRIUM CONSTANTS General reaction at equilibrium Equilibrium constant (Keq) is the ratio or product concentration to reactant concentrations at equilibrium, with each concentration raised to a power equal to the number of moles of that substance in the balanced chemical equation: aA + bB cC +dD → →

EQUILIBRIUM CONSTANTS Value of Keq depends on the temperature of the reaction If temperature changes so does the Keq Size of Keq shows whether the products or reactants are favored Keq > 1: products favored at equilibrium Keq < 1: reactants favored at equilibrium

SAMPLE PROBLEM 18.1 The colorless gas dinitrogen tetroxide (N2O4) and the dark brown gas nitrogen dioxide (NO2) exist in equilibrium with each other: A liter of a gas mixture at equilibrium at 10 °C contains 0.0045 mol N2O4 and 0.030 mol NO2. Writhe the expression for the equilibrium constant and calculate the equilibrium constant (Keq) for the reaction. N2O4(g) 2NO2(g) → →

SAMPLE PROBLEM 18.2 One mole of colorless gas and 1.00 mol of violet iodine vapor are sealed in a 1-L flask and allowed to react at 450 °C. At equilibrium, 1.56 mol of colorless hydrogen iodide is present, together with some of the reactant gases. Calculate Keq for the reaction. H2(g) + I2(g) 2HI(g) → →

SAMPLE PROBLEM Bromine chloride (BrCl) decomposes to form bromine and chlorine according to this equation: At a certain temperature, the Keq for this reaction is 11.1. Suppose that pure BrCl is placed in a 1-L container and allowed to come to equilibrium. The reaction mixture has 4.00 mol Cl2. How many moles of Br2 and Cl2 are present at equilibrium? → 2BrCl(g) Br2(g) + Cl2(g) →