March 7, 2012CHEM 188 – Spring, 2012Hour Exam 2 (Early)March 7, 2012Instructions:Your scantron answer sheet must show your NAME, 7-DIGIT KU ID NUMBER, and LAB SECTION. (Begin these entries at the LEFT end of the space provided.)In answering the questions, be careful to fill in the corresponding circles on the answer sheet according to the number of the question on the exam. USE A SOFT (No. 2) PENCILUseful information: Henderson-Hasselbalch eqn. [acid]base] [conj. log pK pHaQuadratic formula: aacbbx2421. In the reaction CH3COO + HCN  CH3COOH + CN the Brønsted bases areA. CH3COO and HCN B. CH3COO and CH3COOH C. HCN and CND. HCN and CH3COOH E. CH3COO and CN 2. What is the pOH (to the correct number of significant figures) of a solution in which the hydroxide ion concentration is 6.00 x 10 –3 M?A. 2 B. 2.2 C. 2.22 D. 2.222 E. 2.22183. Which of the following statements is true for a 0.10 M solution of a weak acid, HA?A. The pH = 1.00B. The pH > 1.00C. [H+] > [HA]D. [H+] < [A-]E. none of the above 14. Which answer correctly lists all of the weak bases from the following list? 1. LiOH (lithium hydroxide) 2. Mg(OH)2 (magnesium hydroxide) 3. KOH (potassium hydroxide) 4. Al(OH)3 (aluminum hydroxide) 5. CH3NH2 (methyl amine)A. 2 & 5 B. 1 & 4 C. 2, 3 & 4 D. 4 & 5 E. 2, 4 & 55. Calculate the pOH of 0.0050 M Ca(OH)2.A. 1.40 B. 1.70 C. 2.00 D. 2.30 E. 12.006. The Ka for hydrofluoric acid, HF, is 7.1 x 104. Calculate the pH of a 1.25 × 10 −2 M HF solution.A. 2.58 B. 2.99 C. 3.47 D. 5.00 E. 6.257. Estimate the pH of a 250 mL aqueous solution prepared by dissolving 2.5 g of acetic acid (CH3COOH) in water. [Ka = 1.8 x 10–5 for acetic acid]A. 2.16 B. 2.46 C. 2.76 D. 3.06 E. 3.368. The pH of a 0.25 M weak monoprotic acid (HA) solution is 3.50. What is the Ka value for this acid?A. 6.3 x 10 8B. 4.0 x 10 7C. 1.3 x 10 6 D. 4.0 x 10 6E. 1.3 x 10 5 9. Calculate the percent ionization of 0.50 M CH3COOH (acetic acid), given Ka = 1.8 x 10 5.A. 0.60 % B. 1.3% C. 1.9% D. 2.7% E. 3.0%10. How many grams of nitrous acid, HNO2, are required to make 750 mL of an aqueous solution with a pH of 2.35? (Ka = 4.5 x 104 for nitrous acid.)A. 1.1 g B. 1.7 g C. 2.7 g D. 4.2 g E. 6.5 g11. Methylamine (CH3NH2) is a weak base, with Kb = 4.4 x 10 4. Calculate the pH of a 0.010 M solution of CH3NH2.A. 10.32 B. 10.82 C. 11.11 D. 11.17 E. 11.28212. Hydrosulfuric acid (H2S) is a diprotic acid. Its two stages of ionization are: H2S  H+ + HSKa1 = 9.5 x 10 8 HS  H+ + S 2Ka2 = 1 x 10 19Calculate the concentration of S2 in a 0.10 M H2S solution.A. 1 x 10 19 M B. 9.7 x 10 5 M C. 1.2 x 10 4 M D. 0.011 M E. 0.10 M13. Calculate the pH of a 0.25 M NaCN solution, given Ka(HCN) = 4.9 x 10 10.A. 2.65 B. 2.84 C. 7.00 D. 11.16 E. 11.3514. Which of the following is the most acidic solution? [Ka = 4.9 x 1010 for HCN, and Ka = 4.5 x 104 for HNO2.]A. 0.10 M HCN and 0.10 M NaCN B. 0.10 M HCNC. 0.10 M HNO2 D. 0.10 M HNO2 and 0.10 M NaNO2 E. 0.10 M NaNO215. Which of the following mixtures cannot be a buffer solution? 1. H3PO4 and NaH2PO4 2. Na2CO3 and NaHCO3 3. NH4Cl and NaClA. 1 only B. 2 only C. 3 only D. 1 and 2 only E. 1, 2 and 316. A solution is prepared by mixing 500. mL of 0.40 M NaOCl and 500. mL of 0.20 M HOCl. What is the pH of this solution? Ka(HOCl) = 3.2 x 10 –8.A. 6.89 B. 7.19 C. 7.49 D. 7.80 E. 8.1017. You are asked to prepare an acetic acid - sodium acetate buffer solution with a pH of 4.25. What molar ratio of CH3COONa to CH3COOH should be used? [Ka = 1.8 x 105 for CH3COOH]A. 3.2 B. 1.8 C. 0.57 D. 0.32 E. 0.1818. You have 500.0 mL of a buffer solution containing 0.30 M benzoic acid (C6H5COOH) and 0.30 M sodium benzoate (C6H5COONa). What will the pH of this solution be after the addition of 50.0 mL of 1.00 M NaOH solution? [Ka(C6H5COOH) = 6.5  105]A. 4.33 B. 4.49 C. 4.67 D. 4.89 E. 5.23319. Calculate the pH at the equivalence point for the titration of 0.10 M HCl with 1.00 M NH3 (Kb = 1.8 x 10 –5).A. 4.77 B. 4.93 C. 5.13 D. 5.28 E. 5.4120. Calculate the pH of the solution resulting from the addition of 25.0 mL of 0.10 M NaOH to 50.0 mL of 0.10 M HCN (Ka = 4.9 x 10 –10).A. 5.27 B. 6.38 C. 8.71 D. 9.31 E. 11.2421. The molar solubility of AgSCN is 1.0  106 M. What is Ksp for this compound?A. 2.0  106B. 1.0  1011C. 2.0  1011 D. 1.0  1012 E. 2.0  1012 22. The solubility product, Ksp, for PbCl2 is 2.4 x 10 – 4. What is the chloride ion concentration, [Cl],in a saturated solution of PbCl2?A. 6.0 x 10 – 5 M B. 2.4 x 10 – 4 M C. 3.9 x 10 – 3 M D. 7.8 x 10 – 2 M E. 1.2 x 10 – 1 M23. The Ksp for Ag2CO3 is 8 x 1012. What is the concentration of Ag+ in a Ag2CO3 solution that is 0.00010 M in CO32?A. 3 x 10  6 M B. 9 x 10  6 M C. 3 x 10  5 M D. 9 x 10  5 M E. 3 x 10  4 M24. Given that Ksp = 1.1 x 1031 for iron (III) hydroxide, Fe(OH)3, calculate the molar solubility of this compound in a solution buffered at a pH of 6.50.A. 3.5 x 1012 M B. 1.1 x 1010 M C. 3.5 x 109 M D. 1.1 x 107 M E. 3.5 x 106 M25. A 0.25-mole quantity of CuSO4 is added to a liter of 1.0 M NH3 solution. What is the concentrationof Cu2+ at equilibrium? [The formation constant for Cu(NH3)42+ is Kf = 5.0 x 1013.]A. 6.0 x 104 M B. 2.6 x 108 M C. 1.6 x 1013 M D. 1.5 x 1014 M E. 2.4 x 1015