Chemistry Sample Quiz 5 Key

CH115 Quiz # 05 Spring, 2007 Name: _________________________________________ Please circle your lab section: A01 (M - W) A02 (T - R) Possible helpful information: ?G = ?H - T?S; pH = pKa + log[AG]/[HA]; 20 POINTS TOTAL (Do scratch work on a separate sheet of paper. Do not turn in scratch work) Circle the letter which corresponds to the most correct answer. 1. Given the following liquids and their boiling points, which has the highest vapor pressure at its normal boiling point? A) ethanol bp = 78oC B) methanol bp = 65oC C) water bp = 100oC D) benzene bp = 80oC c128) The vapor pressures would all be the same. 2 Which one of the following substances should exhibit hydrogen bonding in the liquid state? A) PH3 B) He C) H2S D) CH4 c128) CH3OH 3. Which of the responses includes all of the following that can form hydrogen bonds with water molecules? 1. Na+ 2. CH3COOH 3. C2H6 4. CH3NH2 A) 1, 2 B) 1, 3 C) 2, 3 c128) 2, 4 E) 3, 4 4. Which response lists all the following pairs that are miscible liquids. Pair # 1. octane (C8H18) and water Pair # 2. acetic acid (CH3COOH) and water Pair # 3. octane (C8H18) and carbon tetrachloride(CCl4) A) 1, 3 B) 1, 2 C) 3 c128) 2, 3 E) 2 5. Calculate the molality of a solution containing 14.3 g of NaCl in 42.2 g of water. (Molar mass of NaCl = 58.44 grams/mole.) A) 2.45 x 10 - 4 m B) 5.80 x 10 - 4 m c128) 5.79 m E) 2.10 m 6. Which of the following solutions has the highest osmotic pressure at 25oC? A) 0.2 M KBr B) 0.2 M ethanol C) 0.2 M Na2SO4 D) 0.2 M KCl c128) 0.2 M AlCl3 7. Calculate the approximate freezing point of a solution made from 21.0 g NaCl and 1.00 x 102 g of H2O. Kf = -1.86oC/m. (NaCl molar mass is 58.44 grams/mole.) A) 3.59oC B) 6.68oC C) -13.4oC c128) -6.68oC E) -3.59oC 8. Which salt produces a basic solution when dissolved in water? A) NaCl B) BaCl2 c128) NaF D) NH4Cl E) KBr 9. The mineral fluorite is composed of CaF2. The molar solubility of calcium fluoride in water is 2.1 x 10-4 moles/L. What is the Ksp of CaF2. c128) 3.7 x 10-11 B) 2.14 x 10-4 C) 4.6 x 10-8 D) 9.8 x 10-12 E) 4.41 x 10-9 10. In which one of the following solutions will acetic acid have the greatest percent ionization? c128) 0.1 M CH3COOH B) 0.1 M CH3COOH dissolved in 1.0 M HCl C) 0.1 M CH3COOH plus 0.1 M CH3COONa D) 0.1 M CH3COOH plus 0.2 M CH3COONa E) 0.1 M CH3COOH dissolved in 1.0 M NaOH 11. Which one of the following salts would form an acidic solution when dissolved in water? A) NaBr B) NaF c128) NaHSO4 D) BaCl2 E) K2CO3 12. Which one of the following combinations cannot be a buffer solution? A) HCN and KCN B) NH3 and (NH4)2SO4 c128) HNO3 and NaNO3 D) HF and NaF E) HNO2 and NaNO2 13. A solution is prepared by mixing 500 mL of 0.10 M NaOCl and 500 mL of 0.20 M HOCl. What is the pH of this solution if the Ka of HOCl is 3.2 x 10-8? A) 4.10 B) 7.00 c128) 7.19 D) 7.49 E) 7.80 14. Which of the following would decrease the Ksp for PbI2? A) Lower the pH of the solution B) Add a solution of Pb(NO3)2 C) Add a solution of KCl D) Increase the pressure c128) None of these, the Ksp of a compound is constant at constant temperature 15. Which of the following species has the highest entropy (SE) at 25EC? (Hint: look at physical state of each.) A) CH3OH(R) c128) CO(g) C) MgCO3(s) D) H2O(R) E) Ni(s) 16. Determine ?SE for the following reaction, SO3(g) + H2O(R) ÿ H2SO4(R) given the following absolute entropies: SE(J/K@mol) SO3 256.2 H2O 69.9 H2SO4 156.9 A) ?SE = 169.3 J/K B) ?SE = 1343.2 J/K c128) ?SE = -169.3 J/K D) ?SE = -29.4 J/K E) ?SE = 29.4 J/k 17. A reaction is spontaneous at all temperatures if A) ?H and ?S are both positive B) ?H and ?S are both negative C) ?H is positive and ?S is negative c128) ?H is negative and ?S is positive E) no correct answer is given 18. Given the following notation for an electrochemical cell: Pt(s) / H2(g)/H+(aq)//Ag+/Ag(s) What is the balanced overall (net ionic) cell reaction? A) 2H+(aq) + 2Ag+(aq) ÿ H2(g) + 2Ag(s) B) H2(g) + 2Ag(s) ÿ H+(aq) + 2Ag+(aq) C) 2H+(aq) + 2Ag(s) ÿ H2(g) + 2Ag+(aq) D) H2(g) + Ag+(aq) ÿ H+(aq) + Ag(s) c128) H2(g) + 2Ag+(aq) ÿ 2H+(aq) + 2Ag(s) 19. Which chemical species undergoes reduction according to the following cell diagram? Sn / Sn2+ // NO3G(acid soln), NO(g)/Pt A) Sn B) Sn2+ c128) NO3G D) NO E) Pt 20. The half-reaction that should occur at the anode during electrolysis of aqueous bromide solution is: A) Br2 + 2eG ÿ 2BrG B) Na ÿ Na+ + eG C) Na+ + eG ÿ Na c128) 2BrG ÿ Br2 + 2eG E) 2H2O ÿ O2 + 4H+ + 4eG William Haag K:\Current Quizzes\quiz 05-0675_key.wpd