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12_new - Homework#9 holcombe(51160 1 This print-out should...

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Homework #9 holcombe (51160) 1 This print-out should have 15 questions. 5 . 2 × 10 19 Multiple-choice questions may continue on 4. the next column or page find all choices 1 . 69 × 10 14 before answering. 5. 001 10.0 points A student titrated a sample containing 102 mL of 0 . 3 M NaOH with 0 . 67 M HCl. What is the pH of the solution after 20 mL of the hydrochloric acid has been added? 1. 7 2. 14 . 16 3. 0 . 84 4. 13 . 16 correct 5. 0 . 16 Explanation: V NaOH = 102 mL [NaOH] = 0 . 3 M V HCl = 20 mL [HCl] = 0 . 67 M Initially n NaOH : (102 mL)(0 . 3 M) = 30 . 6 mmol n HCl : (20 mL)(0 . 67 M) = 13 . 4 mmol NaOH + HCl NaCl ini 30 . 6 mmol 13 . 4 mmol +H 2 O 13 . 4 mmol 13 . 4 mmol fin 17 . 2 mmol 0 mmol V new = 102 mL + 20 mL = 122 mL [NaOH] = 17 . 2 mmol = 0 . 141 M = [OH ] 122 mL pOH = log[OH ] = log(0 . 141) = 0 . 84 pH = 14 pOH = 14 0 . 84 = 13 . 16 002 10.0 points What is K sp for AgI, if its molar solubility is 9 . 1 × 10 9 mol / L? 1. 6 . 9 × 10 9 2. 1 . 4 × 10 21 3. 0.0053 6. 7 . 744 × 10 13 7. 8 . 281 × 10 17 correct Explanation: S = 9 . 1 × 10 9 mol / L The solubility equilibrium is AgI(s) Ag + (aq) + I (aq) [Ag + ] = [I ] = S = 9 . 1 × 10 9 mol / L K sp = [Ag + ][I ] = 9 . 1 × 10 9 2 = 8 . 281 × 10 17 003 10.0 points What is K sp for Ca(OH) 2 , if its molar solu-bility is 0 . 011 mol / L? 1. 5 . 2 × 10 25 2. 1 . 4 × 10 21 3. 5 . 3 × 10 6 correct 4. 1 . 7 × 10 14 5. 6 . 9 × 10 11 6. 4 . 7 × 10 30 7. 8 . 3 × 10 8 Explanation: S = 0 . 011 mol / L The solubility equilibrium is Ca(OH) 2 (s) Ca 2+ (aq) + 2 OH (aq) [Ca 2+ ] = S = 0 . 011 mol / L [OH ] = 2 S = 0 . 022 mol / L
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