Chemistry 112 Name Practice Exam 2B Section

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1 Chemistry 112 Name Practice Exam 2B Section IMPORTANT: On the scantron (answer sheet), you MUST clearly fill your name, your student number, section number, and test form (white cover = test form A; yellow cover = test form B). Use a #2 pencil. There are 25 questions on this exam. Check that you have done all of the problems and filled in the first 25 bubbles on the scantron BEFORE TIME IS CALLED. The maximum score on this exam is 25 points. Your score will be reported in percent (max 100%). Exam policy Calculators with text-programmable memory are not allowed. Relevant data and formulas, including the periodic table, are attached at the end of this exam. Your grade will be based only on what is on the scantron form. The answer key will be posted on ANGEL after the exam. You have 75 minutes to complete this exam. You must completely fill in your scantron bubbles before the 75 minute period has ended. You must turn in your cover sheet with your scantron answer form. Hints As you read the question, underline or circle key words to highlight them for yourself. Avoid errors from "mis-reading" the question. Pay attention to units and magnitudes (decimal places) of numbers obtained from calculations. There is no penalty for guessing. Circle the answer you choose so that you can grade yourself using the answer key posted after the exam.

2 Chem 112 Practice Exam 2B Thermodynamics, Acid/Base Chemistry In the process below, which species are acting as Bronsted acids and bases? H 2 O OH A. acid base acid base B. base acid base acid C. acid base base acid D. acid acid base base E. base acid acid base 2. ΔG for the following reaction is 2879 kj/mol. What is ΔG f for glucose (C 6 H 12 O 6 )? ΔG f of CO 2 (g) is kj/mol and Δ G f of water is kj/mol C 6 H 12 O 6 (s) + 6 O 2 (g) 6 CO 2 (g) + 6 H 2 O(l) ΔG rxn = 2879 kj/mol A kj/mol B kj/mol C kj/mol D kj/mol E kj/mol 3. A demonstration in class illustrated the acidity and basicity of various oxides. Which one of the following oxides produces an basic solution when added to water? A. SiO 2 B. P 4 O 10 C. Al 2 O 3 D. Na 2 O E. Cl 2 O 7

3 4. Which of the following solutions would have a ph < 7? A. iv only B. i and ii C. ii and iii D. i and iv E. i, iii, and iv i. NH 4 Cl (aq) ii. CaF 2 (aq) iii. Al(NO 3 ) 3 (aq) iv. HF (aq) 5. What is the value of ΔG for this reaction at 25 C? K eq = A. +22 kj/mol B. 4.2 kj/mol C. 25 kj/mol D. 50 kj/mol E. 490 kj/mol N 2 (g) + 3 H 2 (g) 2 NH 3 (g) 6. The entropy of vaporization (ΔS vap ) for benzene is 96.4 J/K-mol. The enthalpy of vaporization (ΔH vap ) is 33.9 kj/mol. What is the boiling point of benzene? A C B C C C D. 4.8 C E C

4 7. Solid ammonium nitrate (NH 4 NO 3 ) is highly soluble in water. As demonstrated in class, when it dissolves at 298 K, the solution gets cold (i.e., the beaker feels very cold). Based on this information, what is the temperature dependence of ΔG? A. ΔG is negative at all temperatures. B. ΔG is positive at all temperatures. C. ΔG is positive at low temperature and negative at high temperature. D. ΔG is negative at low temperature and positive at high temperature. E. ΔG is 0; the system is at equilibrium at all temperatures. 8. Which one of the following species cannot be a Lewis base? A. F B. H 2 O C. OH D. NH 3 E. NH Which reaction below should have ΔS > 0? A. 2 H 2 (g) + O 2 (g) 2 H 2 O (g) B. 2 NO 2 (g) N 2 O 4 (g) C. Ag + (aq) + Cl (aq) AgCl (s) D. BaF 2 (s) + H 2 O (l) Ba 2+ (aq) + 2 F (aq) E. 2 Hg (l) + O 2 (g) 2 HgO (s) 10. A chemist adds 300 ml of a 0.34 M solution of HCl to 500 ml of a 0.10 M solution of HClO 4. What is the poh of the resulting solution at 25 C? A B C D E. The poh cannot be determined from the information provided.

5 11. Given the following data for aqueous solutions at 25 C, which one of the answer choices is the strongest acid? Pyridine, C 5 H 5 N (K b = ) Acetic acid, CH 3 COOH (K a = ) Phenol, C 6 H 5 OH (K a = ) Hydrogen cyanide, HCN (K a = ) A. HCN B. C 6 H 5 O C. CH 3 COOH D. C 5 H 5 NH + E. C 6 H 5 OH 12. The concentration of ascorbic acid (vitamin C) in a solution is M at 298 K. What is the ph of the solution? Structure of ascorbic acid For ascorbic acid, K a1 = , K a2 = A. 3.4 B. 4.1 C. 6.7 D. 7.2 E Which of the following will have the highest gas-phase entropy at 25 C? E. C 2 H 2 A. H 2 B. C 2 H 6 C. CH 4 D. C 3 H 8

6 14. Benadryl is an over-the-counter drug that acts as an antihistamine. It is used to treat a number of conditions that include allergies, insomnia, and motion sickness. What is the ph of a M solution of a dose of the liquid form (an aqueous solution) of benadryl at 25 o C? (K b = ) Structure of benadryl: A B C D E Which one of the following salts will form an aqueous solution with the highest ph? A. KIO B. LiBrO C. KClO D. NaClO 2 E. LiClO Which of the following statements are true concerning an aqueous solution of phosphoric acid (H 3 PO 4 )? The acid dissociation constants of H 3 PO 4 (aq) at 298 K are: K a1 = , K a2 = , K a3 = i. The strongest conjugate base involved is the PO 4 3 (aq) species. ii. Both HPO 4 2 (aq) and H 2 PO 4 (aq) species are amphoteric. iii. HPO 4 2 (aq) is a stronger acid than H 2 PO 4 (aq). A. i only B. ii only C. iii only D. i and ii only E. ii and iii only

7 17. Sorbic acid (C 5 H 7 COOH) is a monoprotic weak acid with K a = Its salt (potassium sorbate) is added to cheese to inhibit the formation of mold. What is the ph of a M C 5 H 7 COOK aqueous solution at 25 C? A B C D E K w for water at body temperature (36.9 C) is What is the poh of blood if the ph is 7.40? A. 5.8 B. 6.2 C. 6.6 D. 7.8 E Please rank the following carboxylic acids in order of increasing K a at 25 O C: I. II. III. IV. A. II < III < I < VI B. III < II < I < IV C. IV < II < I < III D. III < IV < I < II E. IV < I < II < III

8 20. According to the figure, which statement is NOT true? A. This substance boils at temperature B. B. ΔS fusion > ΔS evap C. This substance is a liquid between temperatures A and B. D. Increasing the temperature of the gas by 1 K produces a larger value of ΔS than does changing the temperature of the solid by 1 K. E. This substance melts at temperature A. 21. A vinegar and non-standard conditions enthusiast mixes a solution of acetic acid. What is the ΔG of his solution of acetic acid, given the following conditions? (K a of CH 3 COOH = 1.8 x 10 5 ) [CH 3 COOH] = 1M [CH 3 COO ] = 2.0 x 10 4 ph = 4 A KJ/mol B. 8.4 KJ/mol C KJ/mol D KJ/mol E. 8.4 KJ/mol 22. In acidic solution, which statement is TRUE? A. [H 3 O + ] = [OH ] B. [H 3 O + ] = 0 C. [H 3 O + ] > [OH ] D. [H 3 O + ] < [OH ] E. [OH ] =

9 What is K eq of the following reaction? (K a for HNO 2 = 7.2 x 10 4 ) NO 2 (aq) + H 2 O (l) HNO 2 (aq) + OH (aq) A. 7.2 x 10 4 B. 2.7 x 10 8 C. 1.4 x D. 2.7 x 10 4 E. 1.4 x Which of the following statements concerning thermodynamics is / are true? I. Thermodynamics can tell us about the speed of a reaction. II. Thermodynamics can tell us about the extent of a reaction. III. If ΔG o > 0, then K eq > 1. IV. If Q < K eq, then ΔG < 0. A. I and IV only B. III and IV only C. II and IV only D. II, III, and IV only E. All of the above are true After the glucose-phosphate species forms in the metabolic process, the isomerization of glucosephosphate to fructose-phosphate occurs. If the equilibrium constant for the isomerization reaction at 37 C (body temperature) is 0.65, what is the value of ΔG when the ratio of glucose-phosphate to fructosephosphate is 10 to 1? A kj/mol B kj/mol C kj/mol D kj/mol E kj/mol glucose-phosphate fructose-phosphate K eq = END OF EXAM

10 Answer Key: 1. E 2. C 3. D 4. E 5. D 6. E 7. C 8. E 9. D 10. A 11. C 12. A 13. D 14. E 15. A 16. D 17. C 18. B 19. B 20. B 21. D 22. C 23. C 24. C 25. D