7. You have 75.0 mL of 0.10 M HA. After adding 30.0 mL of 0.10 M NaOH, the pH is 5.50. What is the Ka value of HA ?
(A) 2.1 x 10^-6
(B) 3.8 x 10^-6
(C) 4.7 x 10^-2
(D) 7.4 x 10^-8
(E) 6.3 x 10^-4

3. Hydrogen cyanide gas (HCN), a powerful respiratory inhibitor, is highly toxic. It is a very weak acid (Ka =6.2 ×10-10) when dissolved in water. If a 50.0 mL sample of 0.100M HCN is titrated with 0.100 M NaOH, calculate the pH of the solution at the equivalence point of the titration. (A) pH=3.05 (B) pH=8.49 (C) pH=9.21 (D) pH=10.95 (E) pH=11.36

4. Which of the following molecules are nonlinear?NO2–, C2H2, N3–, HCN, CO2, H2O2 , N2O (central atom is N) (A) C2H2, HCN (B)NO2–, H2O2 (C)CO2, N3–(D) N3–, NO2–(E) N2O, H2O2

5. Calculate the concentration of Ag+ in a solution prepared by mixing 150.0 mL 1.0×10－3 M AgNO3 with 200.0 mL 5.00 M Na2S2O3.(K1 = 7.4×108, K2 = 3.9×104) (A) 1.8 x 10-18 mol/L (B) 4.3 x 10-4 mol/L (C) 3.8 x 10-9 mol/L (D) 8.30 x 10-4 mol/L (E) 2.86 x 10-3 mol/L

6. An aqueous solution of 10.00 g of catalase, an enzyme found in the liver, has a volume of 1.00 L at 27℃. The solution’s osmotic pressure at 27℃ is found to be 0.745 torr. Calculate the molar mass of catalase. (A) 3.86 x 108 g/mol (B) 4.15 x 104g/mol (C) 9.8 x 106 g/mol (D) 3.30 x 102g/mol (E) 2.51 x 105 g/mol

8. Which of the following is the correct order for molecules from most to least polar? (A) CH4 > CF2Cl2 > CF2H2 > CCl4 > CCl2H2 (B) CH4 > CF2H2 > CF2Cl2 > CCl4 > CCl2H2 (C) CF2Cl2 > CF2H2 > CCl2H2 > CH4 = CCl4   (D) CF2H2 > CCl2H2 > CF2Cl2 > CH4 = CCl4 (E) CF2Cl2 > CF2H2 > CCl4 > CCl2H2 > CH4

9. Which of the following molecules exhibits chirality? I. 1-chloroethanol II. 2-chloroethanol III. 2-chloropropane IV. 2-chlorobutane V. 3-chloropentane (A) I, III (B) II, IV (C) II, III (D) I, IV (E) II, V

10. At a particular temperature, 12.0 moles of SO3 is placed into a 3.0 L rigid container, and the SO3 dissociates by the reaction 2SO3(g)⇌ 2SO2(g) + O2(g)At equilibrium, 3.0 moles of SO2 is present. Calculate K for this reaction. (A) 0.033 (B) 0.056 (C) 0.44 (D) 0.22 (E) 0.55

11. Assuming that the combustion of hydrogen gas provides three times as much energy per gram as gasoline, calculate the volume of liquid H2 (density = 0.0710 g/mL) required to furnish the energy contained in 80.0 L (about 20 gal) of gasoline (density = 0.740 g/mL). Calculate also the volume that this hydrogen would occupy as a gas at 1.00 atm and 25°C. At 1.00 atm and 25°C, the hydrogen gas needed to replace 20 gal of gasoline occupies a volume of                   L. (A) 277 (B) 19700 (C) 59200 (D) 239000 (E) 977000

12. Consider the following orderings. I. Al＜Si＜P＜Cl        II. Be＜Mg＜Ca＜Sr III. I＜Br＜Cl＜F         IV. Na+ ＜Mg2+＜Al3+＜Si4+Which of these give (s) a correct trend in ionization energy? (A) III (B) I, II (C) I, IV (D) III, IV (E) I, III, IV

13. A 0.739-g sample of an iron ore is dissolved in acid. The iron is then reduced to Fe2+ and titrated with 47.22 mL of 0.02242 M KMnO4 solution. Calculate the results of this analysis in terms of % Fe (55.847 g/mol). (A) 16 (B) 22 (C) 32 (D) 40 (E) 50