UMass Amherst CHEM 112 - Chem 112 Exam 3 Review (3 pages)

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Chem 112 Exam 3 Review



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Chem 112 Exam 3 Review

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3
School:
University of Massachusetts Amherst
Course:
Chem 112 - Gen Chem-Sci
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Exam 3 Review Which of the following chemical equations corresponds to K b1 for SO 3 2 A SO 3 2 aq H 2 O B H 2 SO 3 aq OH aq HSO 3 aq OH aq HSO 3 aq H 2 O C HSO 3 aq H 2 O H 2 SO 3 aq OH aq D SO 3 2 aq H3O aq HSO3 aq H2O L E HSO 3 aq OH aq SO 3 2 aq H 2 O Which of the following species is the strongest acid in an aqueous solution A CH 3 CO 2 H B CH 3 CH 2 CO 2 H C CH 2 ClCO 2 H D CHCl 2 CO 2 H E CCl 3 CO 2 H What is the pH of the solution which results from mixing 33 8 mL of 0 512 M HF aq and 33 8 mL of 0 512 M NaOH aq at 25 C K a of HF 7 2E 4 A 8 17 B 8 28 C 8 37 D 5 72 E 10 6 All of the following compounds are acids containing chlorine Which compound is the weakest acid A HClO2 B HCl C HClO D HClO3 E HClO4 If the ratio of base to acid in a buffer is decreased by a factor of 10 the buffer pH decreases by Which one of the following conditions is always true for a titration of a weak acid with a strong base A If a colored indicator is used it must change color rapidly in the weak acid s buffer region B A colored indicator with a pKa less than 7 should be used C The equivalence point occurs at a pH greater than 7 D The equivalence point occurs at a pH equal to 7 E Equal volumes of weak acid and strong base are required to reach the equivalence point Which of the following equations is the solubility product for Cu II hydroxide Cu OH 2 Exam 3 Review What mass of KCl molar mass 74 55 g mol must be added to 1 03 L of 1 92E 2 M Pb 2 aq to initiate precipitation of PbCl 2 s The K sp of PbCl 2 is 1 7E 5 Assume no volume change occurs upon addition of KCl A 1 11 g B 2 28 g C 2 22 g D 4 11E 4 g E 1 14 g The K a of bicarbonate ion HCO 3 is 4 8E 11 What base acid ratio is necessary to make a buffer with a pH of 10 7 A 1 46 B 2 41 C 0 381 D 24 1 E 0 416 Which of the following combinations would be best to buffer an aqueous solution at a pH of 7 0 A HNO 2 and NO 2 K a 4 5E 4 B CH3CO2H and CH3COO Ka 1 8E 5 C H 2 PO 4 and HPO 4 2 Ka2 6 2E 8 D H3PO4 and H2PO4 Ka1 7 5E 3 E NH4 and NH3 Ka 5 7E 10 What is the pH of a buffer that results when 0 489 mol NaHCO 2 is mixed with 76 9 mL of 0 361 M HCl aq and diluted with water to 466 mL K a of HCO 2 H 1 8E 4 A 2 52 B 4 97 C 4 97 D 3 74 E 4 21 What is the OH concentration in 0 516 M CH 3 CO 2 aq K b of CH 3 CO 2 5 6E 10 A 2 89E 10 M B 1 70E 5 M C 1 79E 9 M D 1 79E 5 M E 3 04E 4 M An acid base equilibrium system is created by dissolving 0 50 mol CH3CO2H in water to a volume of 1 0 L What is the effect of adding 0 50 mol CH3CO2 aq to this solution 1 The pH of the solution will equal 7 00 because equal concentrations of a weak acid and its conjugate base are present 2 Some CH3CO2H aq will ionize increasing the concentration of CH3CO2 aq and increasing the pH 3 Some CH3CO2 aq will react with H3O increasing the concentration of CH3CO2H aq and reestablishing the solution equilibrium A 3 only B 1 2 and 3 C 1 only D 2 only E 1 and 3 All of the following statements concerning acid base buffers are true EXCEPT A buffers are resistant to changes in pH when diluted with water B the pH of a buffer is close to the pKa of the weak acid from which it is made C buffers contain appreciable quantities of a weak acid and its conjugate base Exam 3 Review D buffers are used as colored indicators in acid base titrations E buffers are resistant to pH changes upon addition of small quantities of strong acids or bases Which of the following conditions is are met at the equivalence point of the titration of a monoprotic weak base with a strong acid 1 The moles of acid added from the buret equals the initial moles of weak base 2 The volume of acid added from the buret must equal the volume of base titrated 3 The pH of the solution is less than 7 00 A 1 only B 2 and 3 C 1 and 3 D 2 only E 3 only What is the pH of a solution that results from adding 120 mL of 0 115 M HCl to 120 mL of 0 150 M NH 3 K b of NH 3 1 8E 5 A 5 27 B 9 26 C 9 78 D 4 22 E 8 73 What is the result of mixing equal molar quantities of a strong acid with a weak base A neutral solution B a basic solution C a neutralization reaction with heat produced D a salt solution with a pH dependent on the ratio of Ka and Kb E an acidic solution The solubility of BaCrO 4 s in water is 3 30 milligrams in 0 972 L at a given temperature What is the value of K sp for BaCrO 4 The molar mass of BaCrO 4 is 253 37 g mol A 1 80E 4 B 1 34E 5 C 1 80E 10 D 2 68E 5 E 1 70E 10 To make a buffer with a pH of 8 00 you should use a weak acid with a K a close to A 22 7 mL sample of vinegar is titrated with 0 512 M NaOH aq If the titration requires 36 6 mL of NaOH aq to reach the equivalence point what is the concentration of acetic acid in the vinegar A 1 87E 2 M B 0 846 M C 0 826 M D 0 318 M E 0 805 M


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