Problem Sets 10 11 Chapter 18 Buffers Ksp and Titrations Set 10 1 The H3O concentration of a 0 10M solution of acetic acid decreases when which of the following substances are added a d NaCl two of the three choices above b KOH c sodium acetate e all three choices 2 Which of the following mixtures will be a buffer when dissolved in 1 liter of water a 0 10 mol Ba OH 2 and 0 20 mol HCl b 0 30 mol KCl and 0 30 mol HCl c 0 40 mol NH3 and 0 40 mol HCl d 0 20 mol HNO2 and 0 10 mol NaOH e 0 20 mol HBr and 0 10 mol KOH 3 Which of the following is the most effective buffer system for a pH value of 7 45 Use Table 17 3 for data and assume all concentrations are 1M a Carbonic acid and sodium bicarbonate b Sodium bicarbonate and sodium carbonate c Sodium dihydrogen phosphate and disodium hydrogen phosphate d Hydrogen cyanide and sodium cyanide e Ammonia and ammonium chloride 4 If you add 0 35 g NaF to 150 mL of a 0 30 M HF what is the pH of the resulting solution Use Table 17 3 for data a 2 41 b 3 15 c 3 90 d 4 21 e 5 55 You have 250 0 mL of a 0 56M solution of sodium acetate How many mL of 5 0 50M acetic acid should be added to make a buffer of pH 4 40 6 7 a 200 b 250 c 600 d 700 e 750 For an acetic acid sodium acetate buffer to have a pH of 4 64 what molar ratio of CH3COOH to Na CH3COO is needed a 0 60 b 0 80 c 1 25 d 1 70 e 2 00 Which of the following statements is true of the titration of a weak monoprotic acid by a strong base such as NaOH a b c d e At the equivalence point the pH 7 The moles of acid are greater than the moles of base at the equivalence point The moles of base are greater than the moles of acid at the equivalence point The moles of acid equals the moles of base at the equivalence point Answer b or answer c or answer d plus answer a 8 A 25 0 mL sample of 0 200M HF aq was titrated with 0 200M NaOH What was the pH at the equivalence point a 5 93 b 7 00 c 8 07 d 10 86 e 3 14 9 Which of the following conditions is always true for a titration of a weak acid with a strong base 1 Equal volumes of acid and base are required to reach the equivalence point 2 The pH when half the acid has been titrated the pKa of the acid 3 An indicator for this titration must change color before pH 7 a Only one of these 1 only or 2 only or 3 only b c d e All three 1 and 2 1 and 3 2 and 3 ANSWERS SET 10 1 D 2 D 3 C 4 A 5 C 6 C 7 D 8 C 9 A Set 11 1 The solubility product expression for mercury I iodide Hg2I2 is Ksp 2 What is the molar solubility of Al OH 3 at 25 oC given that its solubility product Ksp 5 0 X 10 33 a b c d e Hg2 I 2 2 2I 2 Hg2 2 I 2 Hg2 2 2I Hg2 Hg 2I 2 a 8 4 X 10 9 b 2 8 X 10 9 c 3 7 X 10 9 d 1 4 X 10 9 e none of the above values a 8 X 10 9 M b 2 X 10 9 M c 3 X 10 5 M d 6 X 10 5 M e 8 X 10 4 M 3 The Ksp for silver I carbonate is 8 X 10 12 What is the approximate Ag in a saturated solution of silver I carbonate that is 0 010M in CO3 2 4 What is the minimum concentration of Mg2 that is needed to begin the formation of a precipitate of magnesium hydroxide in a solution of pH 10 5 The Ksp for magnesium hydroxide is 6 X 10 12 a 2 X 10 5 M b 6 X 10 5 M c 4 X 10 5 M d 2 X 10 8 M e 6 X 109 M 5 Ksp for Fe IO3 3 is 10 14 Two solutions one being iron III nitrate and the other being sodium iodate were mixed At the instant of mixing Fe3 10 4M and IO3 10 5M What happens a A precipitate forms because Qsp Ksp b A precipitate forms because Qsp Ksp c No precipitate forms because Qsp Ksp d No precipitate forms because Qsp Ksp 6 The insoluble salts AV B2W C2X3 DY2 and EZ3 which were formed from the metal ions A B C3 D2 and E3 and the nonmetal ions V1 W2 X2 Y1 and Z1 all have the same Ksp value The salt with the highest molar solubility is 7 The solubility product expression for Fe OH 3 is Ksp 8 Given the Ksp data below determine the order of solubility order of the three salts AV a b B2W c C2X3 d DY2 e EZ3 a b c d e Fe3 OH Fe2 OH 2 Fe OH 3 Fe3 OH 3 Fe3 3OH 3 AgCl Ag2CO3 Ag3PO4 Ksp 1 0 X 10 10 6 3 X 10 12 2 0 X 10 21 a AgCl Ag2CO3 Ag3PO4 b Ag2CO3 Ag3PO4 AgCl c Ag2CO3 AgCl Ag3PO4 d Ag3PO4 Ag2CO3 AgCl e AgCl Ag3PO4 Ag2CO3 9 A saturated solution of a certain metal II chloride has a chloride ion concentration of 0 032M The Ksp for this compound can be determined to be a 2 6 X 10 7 b 4 1 X 10 6 c 1 6 X 10 5 d 2 6 X 10 4 e 1 6 X 10 2 10 What is the pH of a saturated solution of lead II hydroxide The Ksp 4 0 X 10 15 a 4 7 b 7 2 c 9 0 d 9 1 e 9 3 ANSWERS TO SET 11 1 C 2 C 3 C 4 B 5 D 6 C 7 D 8 C 9 C 10 E