Chem 1202 Form 2 Answer Key Fall 2024 Dr Gasery Exam 2 Chapters 16 and 17 1 17 2 Acid Base Equilibria and Aqueous Equilibria Common Ion Effect and Buffers Instructions Use an 8 5 x 11 inch green and white scantron On Side Two of the scantron 1 Print your Last Name then First Name and bubble it in 2 Print and bubble in your complete correct LSU ID number 89 number 3 Bubble 2 in the Grade or Education box On Side One of the scantron 1 Print your name 2 Answers to the exam questions must go on side one Bubble the answers on 3 There is exactly one best answer for each question and you should NOT the scantron sheet using a pencil leave a question blank 4 On a numerical question choose the response closest to the correct answer This exam is closed notes and closed book You are not allowed to use your own scratch paper Only a scientific calculator is allowed during the exam NO graphing calculators Mark your answers in your Exam for future reference You can keep your Exam for further study Present your LSU ID and the front of your exam when submitting your scantron Useful Information and Constants The periodic table is located at the back of the exam Kw 1 0 x 10 14 Molarity mol L pH pKa log ionization H equilibrium HA initial x 100 base acid 1 1 Which of the following compounds will produce the weakest conjugate base a Triflic acid CF3SO3H b Acetic acid CH3COOH c Boric acid H3BO3 d Pyridine C5H5N e Lithium diisopropylamide LDA pKa 35 pKa 15 pKa 4 76 pKa 9 15 pKa 5 23 Stronger acid weaker conjugate base Lower pKa stronger acid pKa values can be negative 2 Benzoic acid C6H5COOH is a weak acid which has a Ka of 6 3 x 10 5 If a 0 020 M solution of benzoic acid is prepared calculate the percent ionization of the acid a 7 15 b 3 82 c 1 65 d 5 61 e 6 52 3 What is the pH of a 3 50 x 10 3 M HNO3 solution at 25 C pH log H HNO3 is a strong acid pH log 3 50 x 10 3 a 5 93 b 10 8 c 7 93 d 2 46 e 11 6 4 The pH of a 0 40 M aqueous solution of propionic acid C2H5COOH at 25oC At equilibrium the resulting pH was 2 65 What is the value of Ka for propionic acid a 7 53 x 10 7 b 8 29 x 10 13 c 1 26 x 10 5 d 1 96 x 10 9 e 5 29 x 10 11 5 Of the following substances an aqueous solution of which substance s will form basic KCN LiBr NaF NaNO3 solutions NH4Cl a KCN and NaF b NaNO3 and NaF c NH4Cl and NaNO3 d KCN NaNO3 and LiBr e LiBr NH4Cl and NaF 2 6 Hydrobromic acid HBr is a strong acid Which of the following statements is TRUE regarding this acid a HBr does not dissociate at all when dissolved in water b Aqueous solutions of HBr contain equal concentrations of H3O and OH c HBr cannot be neutralized by a strong base d HBr dissociates completely to H3O and Br when it is dissolved in water e HBr produces a gaseous product when it is neutralized 7 Determine whether the pH increases decreases or stays the same when the first substance mentioned in each of the multiple choices is added to a solution of the second substance and then pick the correct statement a When NaCl is added to a solution of NaOH the pH increases b When HCl is added to a solution of CH3COOH the pH decreases c When HF is added to a solution of NaF the pH stays the same d When NaOH is added to a solution of HNO3 the pH stays the same e When HNO3 is added to a solution of NaCl the pH stays the same 8 A solution of hydroazoic acid HN3 a weak acid has a concentration of 0 50 M What is the pH of this solution The Ka of HN3 is 1 9 x 10 5 a 9 85 b 0 30 c 8 60 d 5 73 e 2 51 likely be classified as which of the following a A weak base b A weak acid c A strong base d A strong acid e A salt 9 An aqueous solution of a particular compound has a pH of 7 46 The compound can most 10 In the gaseous reaction below which is NH3 acting as in the reaction NOTE There is only one product in this reaction Analyze the reaction based on this fact a Bronsted Lowry acid b Bronsted Lowry base c Lewis base d Lewis acid e Arrhenius acid Since there is only 1 product shown the NH3 molecule acts as an electron pair donor Lewis base and H acts as an electron pair acceptor Lewis acid 3 11 What is the pH of an aqueous solution at 25 0 C that contains 1 35 10 8 M hydroxide pOH log 1 35 x 10 8 7 869666 pH 14 7 869666 6 13 12 The pH of a 0 25 M aqueous solution of hydrofluoric acid HF at 25 0 C is 2 03 What is ion a 7 87 b 8 00 c 6 13 d 1 35 e 7 00 the value of Ka for HF a 2 0 x 10 9 b 1 1 x 10 9 c 6 0 x 10 5 d 3 5 x 10 4 e None of the above 13 Which one of the following pairs cannot be mixed to form a buffer solution a NH3 NH4Cl b NaC2H3O2 HCl C2H3O2 c RbOH HBr d KOH HF e H3PO4 KH2PO4 acetate ion Strong base and strong acid combination cannot act as a buffer solution 14 Calculate the pH of a solution prepared by dissolving 0 150 mol of benzoic acid and 0 300 mol of sodium benzoate in water sufficient to yield 1 00 L of solution The Ka of benzoic acid is 6 30 x 10 5 a 2 516 b 3 892 c 4 502 d 10 16 e 4 20 15 If the pH of a buffer solution is equal to the pKa of the acid in the buffer what does this tell you about the relative concentration of the acid and the conjugate base forms of the buffer components a The acid concentration must be zero b The base concentration must be zero c The acid and base concentrations must be equal d The acid and base concentrations must be equal to the Ka e The base concentration must be 2 3 times as large as the acid concentration 4 16 What is the pH of a 0 28 M ascorbic acid Ka1 8 0 x 10 5 and Ka2 1 6 x 10 12 a 2 04 b 2 32 c 2 82 d 4 65 …