Learning Goals • identify common equilibrium constants, including Keq, Ksp, Kw, Ka, Kb and write the expressions for each • solve problems related to equilibrium by performing calculations involving concentrations of reactants and products Equilibrium Law • mathematical description of chemical system at equilibrium • defined by the equilibrium constant, K • Complete Inv. 7.2.1 on p. 473-474 Writing Equilibrium Law Equations For aA + bB cC + dD, K = [C]c[D]d [A]a[B]b (omit units) • omit (s) and (l) • include only (aq) and (g) Ex. H2(g) + S(l) H2S(g) Ex. NH3(g) + H2O(l) NH4+(aq) + OH-(aq) p. 431 #1-3, p. 434 #1 Calculating K • Write the equilibrium law equation. • Substitute [ ]eq • K can be used to predict the equilibrium position (Review Equilibrium Position table in lesson 1 and add a column for K.) • Sample Problem 2 (p. 430) In a closed vessel at 500°C, N2(g) + 3 H2(g) 2 NH3(g) The equil. conc. of N2, H2 and NH3, respectively, are 1.50 x 10-5 M, 3.45 x 10-1 M and 2.00 x 10-4 M. Calculate K. • Sample Problem 3 (p. 431) In a closed vessel at 500°C, 2 NH3(g) H2(g) N2(g) + 3 The equil. conc. of N2, H2 and NH3, respectively, are 1.50 x 10-5 M, 3.45 x 10-1 M and 2.00 x 10-4 M. Calculate K. K (synthesis of ammonia) K’ (decomposition of ammonia) Mathematical relationship b/w K and K’? K = 1/K’ What does the magnitude of K tell us about the equilibrium position? A. In a closed system at 25°C, 2 CO(g) + O2(g) 2 CO2(g) K = 3.3 x 1091 B. Decomposition of water at 1000°C, 2 H2O(g) 2 H2(g) + O2(g) K = 7.3 x 10-10 C. NO2(g) + NO(g) N2O(g) + O2(g) K = 0.951 Homework • p. 436 #1-6