18. A 0.15 M solution of a weak acid is 3.0% dissociated. The K_a of the acid is calculated to be .
(A) 3.5 × 10^-4
(B)4.2 × 10^-3
(C) 1.4 × 10^-4
(D) 2.4 × 10^-2
(E)3.6 × 10^-3

14. Consider the reaction 3A + B + C D + E where the rate law is defined as –(∆[A]/∆t) = k[A]2 [B][C]. An experiment is carried out where [B]0 = [C]0 = 1.00 M and [A]0 = 1.00 × 10-4 M. We also know that after 3.00 min of the reaction, [A]is 3.26 × 10-5 M. What will be the concentration of A after 10.0 min? (A) 1.27 × 10-5 M (B)2.5 × 10-6 M (C) 1.00 M (D) 2.50 × 10-5 M (E)7.90 × 10-5

15. Ea for the uncatalyzed reaction O3(g) + O(g) → 2O2 is 14.0 kJ. Ea for the same reaction when catalyzed is 11.9 kJ. What is the ratio of the rate constant for the catalyzed reaction to that for the uncatalyzed reaction at 25℃? Assume that the frequency factor A is the same for each reaction. (A) 215 (B)51 (C) 2.3 (D) 532 (E)0.25

16. Consider the decomposition equation of a compound: C5H6O3(g) C2H6(g) + 3CO(g). When a 5.63-g sample of pure C5H6O3(g) was sealed into an otherwise empty 2.50-L flask and heated to 200℃, the pressure in the flask gradually rose to 1.63 atm and remained at that value. The K value for this reaction is . (A) 3.89 × 10-1 (B)6.74 × 10-6 (C) 8.00 × 10-2 (D) 4.00 × 10-3 (E)1.20 × 10-9 

17. Which of the following 0.10 M solutions are correctly arranged in order of most acidic to most basic? (A) HCl > KCl > NH4Cl > KCN > KOH (B)NH4Cl .> HCl .> KCl > KCN > KOH (C) NH4Cl .> HCl .> KCN > KCl > KOH (D) HCl > NH4Cl > KCl > KCN > KOH (E)HCl > NH4Cl > KCN > KCl > KOH

19. Two drops of indicator HIn (Ka = 1.0 × 10-9 ), where HIn is yellow and In- is blue, are placed in 100.0 mL of 0.10 M HCl. The solution is titrated with 0.10 M NaOH. At what pH will the color change (yellow to greenish yellow) occur? (A) 7.0 (B)8.5 (C) 9.0 (D) 7.5 (E)8.0

20. The solubility of Fe(OH)3 (Ksp = 4 × 10-38) in a solution buffered at pH = 5.0 is mol/L (A) 4.0 × 10-11 (B)2.5 × 10-10 (C) 2.5 × 10-4 (D) 4.0 × 10-29 (E)4.0 × 10-17

21. Which of the following statements is correct? (A) For HCl(g) → H+ (aq) + Cl- (aq), its ∆So is larger than 0 (> 0) (B)The So of Cgraphite(s) is larger than the So of Cdiamond(s) (C) One mol H2 (at STP) has more positional probability than 1 mol H2 at 100 K, 0.5 atm. (D) The sign of ∆Ssurr for the process of I2(g) → I2(s) is negative (-). (E)At constant T and P, the change with ∆Η = +25 kJ, ∆S = +100 J/K, T = 300. K is not a spontaneous process.

22. Consider the following reaction at 25°C: 2NO2(g) N2O4(g). The values of ∆Ηο and ∆Sο are -58.03 kJ/mol and -176.6 J/K•mol, respectively. Assuming ∆Η ο and ∆Sο are temperature independent, estimate the value of K at 100.0°C. (A) 3.00 × 106 (B)1.47 × 10-87 (C) 8.72 (D) 7.89× 10-2 (E)5.9 × 1015

23. An unknown metal M is electrolyzed. It took 74.1 s for a current of 2.00 A to plate out 0.107 g of the metal from a solution containing M(NO3)3. The metal is therefore identified as________ . (A) aluminum (B)cobalt (C) bismuth (D) lead (E)gallium

24. The atomic mass of 1 H is 1.00782 amu and the mass of a neutron is 1.00866 amu. The binding energy for uranium-235 (atomic mass 235.0439 u) is calculated to be___________ J/nucleon. (A) 1.22 × 10-11 (B)1.22 × 10-12 (C) 1.22 × 10-13 (D) 1.47 × 10-12 (E)1.47 × 10-11