13. Calculate the pH of a 0.05 M NaCN solution. The pKa value for HCN is 9.2 .
(A) pH=5.25
(B) pH=3.05
(C) pH=11.83
(D) pH=10.95
(E) pH=8.75

9. Consider the titration of 100.0 mL of 0.100 M C2H5NH2 () by 0.200 M HCl at 25.0℃. Calculate the pH of the resulting solution after the 25.0mL of 0.200 M HCl has been added. (A) pH=1.83 (B) pH=3.25 (C) pH=8.24 (D) pH=12.17 (E) pH=10.75

10. A chemist needs a solution buffered at pH 5.0 and can choose from the following acids (and their sodium salts): Which system will work best? (A) propanoic acid (B) chloroacetic acid (C) benzoic acid (D) hypochlorous acid (E) salicylic acid

11. In the Lewis structure for xenon dichloride, how many lone pairs of electrons are around the central xenon atom? (A) 1 (B) 2 (C) 3 (D) 4 (E) 5

12. Calculate the root mean square velocity of CH4 (g) molecule at 546K. (A) 29.2 m/s (B) 922.6 m/s (C) 91.7 m/s (D) 2.9 m/s (E) 532.7 m/s

14. A solution is prepared by mixing 100.0 mL of M magnesium nitrate and 200.0 mL of M sodium fluoride. Calculate the concentration of magnesium ion at equilibrium with solid magnesium fluoride  . (A)M (B)M (C)M (D)M (E)M

15. Which of the following sets of molecular structure are incorrect?I. selenium trioxide: T-shaped structureII. silicon tetrafluoride: tetrahedral structureIII. xenon tetrafluoride: tetrahedral structureIV. arsenic pentachloride: trigonal bipyramidal structureV. nitrite ion: V-shaped structure(A) III, V (B) II, III, V (C) I, II, III,V (D) I, III (E) I, IV, V

16. A 1.37 M solution of citric acid (H3C6H5O7) in water has a density of 1.10 g/cm3. Calculate the mole fraction of the citric acid. Citric acid has three acidic protons. (A) 0.056 (B) 0.0035 (C) 0.084 (D) 0.0093 (E) 0.028

17. A 30.00-mL of a mixture that is 0.1500 M in hydrochloric acid and 0.0500 M in nitrous acid is titrated with 0.1000 M sodium hydroxide. Calculate the pH of the resulting solution after the 8.00 mL of 0.1000 M sodium hydroxide has been added. (A) 1.01 (B) 2.10 (C) 3.45 (D) 4.39 (E) 8.33

18. What volume of 2.0 M sodium hydroxide must be added to 200.0 mL of 1.00 M glycolic acid to produce a buffer solution having a pH of 4.00? (pKa for glycolic acid is 3.83) (A) 67.6 mL (B) 148 mL (C) 59.7 mL (D) 78.6 mL (E) 83.3 mL

19. When 1.00 L of 1.00 M barium nitrate solution at 25.0℃ is mixed with 1.00 L of 1.00 M sodium sulfate solution at 25.0℃ in a calorimeter, the white solid barium sulfate forms, and the temperature of the mixture increases to 32.1℃. Assuming that the calorimeter absorbs only a negligible quantity of heat, the specific heat capacity of the solution is 4.18 J/℃ · g, and the density of the final solution is 1.0 g/mL, calculate the enthalpy change per mole of barium sulfate formed. (A) 59 KJ/mol (B) -59 KJ/mol (C) 30 KJ/mol (D) -30 KJ/mol (E) 89 KJ/mol