Acids and Bases Chapter 16 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Acids Have a _________ taste. Vinegar owes its taste to acetic acid. Citrus fruits contain citric acid. React with certain metals to produce ______________ gas. React with carbonates and bicarbonates to produce ______________ ______________ gas Have a __________ taste. Feel ________________. Many soaps contain bases. Bases 16.3 _________ acid is a substance that produces H + (H 3 O + ) in water _________ base is a substance that produces OH - in water 16.3 A __________________ acid is a proton donor A __________________ base is a proton acceptor acidbaseacidbase 16.1 acid conjugate base base conjugate acid O H H+ O H H O H HH O H - + [] + Acid-Base Properties of Water H 2 O (l) H + (aq) + OH - (aq) H 2 O + H 2 O H 3 O + + OH - acid conjugate base base conjugate acid 16.2 __________________ of water H 2 O (l) H + (aq) + OH - (aq) The Ion Product of Water K c = [H + ][OH - ] [H 2 O] [H 2 O] = constant K c [H 2 O] = K w = [H + ][OH - ] The __________________(K w ) is the product of the molar concentrations of H + and OH - ions at a particular _______________________. At 25 0 C K w = [H + ][OH - ] = __________ [H + ] = [OH - ] [H + ] > [OH - ] [H + ] < [OH - ] Solution Is 16.2 What is the concentration of OH - ions in an HCl solution whose hydrogen ion concentration is 1.3 M? K w = [H + ][OH - ] = _____________ [H + ] = _____________M [OH - ] = KwKw [H + ] == _____________ M 16.2 pH A Measure of Acidity pH = _______________________ [H + ] = [OH - ] [H + ] > [OH - ] [H + ] < [OH - ] Solution Is neutral acidic basic [H + ] = 1 x [H + ] > 1 x [H + ] < 1 x pH At 25 0 C 16.3 pH[H + ] pH[H + ] 16.3 pOH = -log [OH - ] [H + ][OH - ] = K w = _____________ -log [H + ] log [OH - ] = ________ pH + pOH = _____________ pHs of some common fluids The pH of rainwater collected in a certain region of the northeastern United States on a particular day was What is the H + ion concentration of the rainwater? pH = - log [H + ] [H + ] = 10 -pH = = _____________ M antilog (pH) = -antilog (-log [H + ]) antilog = [H + ] The OH - ion concentration of a blood sample is 2.5 x M. What is the pH of the blood? pH + pOH = _________ pOH = -log [OH - ]= -log (2.5 x )= _________ pH = pOH = 6.60 = _________ 16.3 Strong Electrolyte = __________________________ NaCl (s) Na + (aq) + Cl - (aq) H2OH2O Weak Electrolyte = __________________________ CH 3 COOH CH 3 COO - (aq) + H + (aq) Strong Acids are strong electrolytes HCl (aq) + H 2 O (l) H 3 O + (aq) + Cl - (aq) HNO 3 (aq) + H 2 O (l) H 3 O + (aq) + NO 3 - (aq) HClO 4 (aq) + H 2 O (l) H 3 O + (aq) + ClO 4 - (aq) H 2 SO4 (aq) + H 2 O (l) H 3 O + (aq) + HSO 4 - (aq) 16.4 HF (aq) + H 2 O (l) H 3 O + (aq) + F - (aq) Weak Acids are weak electrolytes HNO 2 (aq) + H 2 O (l) H 3 O + (aq) + NO 2 - (aq) HSO 4 - (aq) + H 2 O (l) H 3 O + (aq) + SO 4 2- (aq) H 2 O (l) + H 2 O (l) H 3 O + (aq) + OH - (aq) Strong Bases are strong electrolytes NaOH (s) Na + (aq) + OH - (aq) H2OH2O KOH (s) K + (aq) + OH - (aq) H2OH2O Ba(OH) 2 (s) Ba 2+ (aq) + 2OH - (aq) H2OH2O 16.4 F - (aq) + H 2 O (l) OH - (aq) + HF (aq) Weak Bases are weak electrolytes NO 2 - (aq) + H 2 O (l) OH - (aq) + HNO 2 (aq) Conjugate acid-base pairs: The conjugate base of a strong acid has no measurable strength. H 3 O + is the strongest acid that can exist in aqueous solution. The OH - ion is the strongest base that can exist in aqueous solution. 16.4 Relative Strengths of Conjugate Acid-Base Pairs Strong AcidWeak Acid 16.4 What is the pH of a 2 x M HNO 3 solution? HNO 3 is __________________________. HNO 3 (aq) + H 2 O (l) H 3 O + (aq) + NO 3 - (aq) pH = -log [H + ] = -log [H 3 O + ] = -log(0.002) = _______ Start End M 0.0 M 16.4 What is the pH of a 1.8 x M Ba(OH) 2 solution? Ba(OH) 2 is a strong base 100% dissociation. Ba(OH) 2 (s) Ba 2+ (aq) + 2OH - (aq) Start End M M0.0 M pH = pOH = log(0.036) = _______ 16.4 HA (aq) + H 2 O (l) H 3 O + (aq) + A - (aq) Weak Acids (HA) and Acid Ionization Constants HA (aq) H + (aq) + A - (aq) K a = K a is the acid ionization constant KaKa weak acid strength 16.5 Ionization Constants of Some Weak Acids and Their Conjugate Bases at 25C What is the pH of a 0.5 M HF solution (at 25 0 C)? HF (aq) H + (aq) + F - (aq) K a = [H + ][F - ] [HF] = 7.1 x HF (aq) H + (aq) + F - (aq) Initial (M) Change (M) Equilibrium (M) x-x+x+x +x+x K a = = __________ Ka Ka 0.50 x 0.50 K a