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Chapter 16 Acids and Bases 325 Assume that x is small compared to 0.500. = (1.8 X 10⁻⁵) (0.500) x = 0.00300 0.00300 % ionization = 0.500 100% = 0.60% ionized Check: The units (%) are correct. The magnitude of the answer makes sense since we have a weak acid (small K). (c) Given: 0.100 M HC₂H₃O₂, = 1.8 X 10⁻⁵ Find: % ionization Conceptual Plan: Write a balanced reaction. Prepare an ICE table, represent the change with x, sum the table, determine the equilibrium values, put the equilibrium values in the equilibrium expression, solve for x, and then x % ionization. % ionization = X 100% Solution: HC₂H₃O₂(aq) + H₂O(l) 11 H₃O⁺(aq) + C₂H₃O₂⁻(aq) Initial 0.100 0.0 0.0 Change -x +x +x Equil 0.100 x x x Kₐ = [HC₂H₃O₂] = (0.100 (x)(x) = 1.8 X 10⁻⁵ Assume that x is small compared to 0.100. = (1.8 X (0.100) x = 0.00134 0.00134 % ionization = 0.100 X 100% = 1.3% ionized Check: The units (%) are correct. The magnitude of the answer makes sense since we have a weak acid (small K). (d) Given: 0.0500 M = 1.8 X 10⁻⁵ Find: % ionization Conceptual Plan: Write a balanced reaction. Prepare an ICE table, represent the change with x, sum the table, determine the equilibrium values, put the equilibrium values in the equilibrium expression, solve for x, and then x % ionization. % ionization = [HC₂H₃O₂] x X 100% Solution: HC₂H₃O₂(aq) + H₃O⁺(aq) + C₂H₃O₂⁻(aq) Initial 0.0500 0.0 0.0 Change -x +x +x Equil 0.0500 x x = [HC₂H₃O₂] = (0.0500 (x)(x) = 1.8 X 10⁻⁵ Assume that x is small compared to 0.0500. = (1.8 X (0.0500); x = 9.49 X 10⁻⁴ % ionization = 9.49 0.0500 100% = 1.9% ionized Check: The units (%) are correct. The magnitude of the answer makes sense since we have a weak acid (small K). 16.75 Given: 0.148 M HA, 1.55% dissociation Find: Kₐ Conceptual Plan: M [H₃O⁺] and then write a balanced reaction, determine equilibrium concentration, and plug into the equilibrium expression. Copyright © 2017 Pearson Education, Inc.