20. The solubility of Fe(OH)₃ (K_sp = 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

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

18. A 0.15 M solution of a weak acid is 3.0% dissociated. The Ka 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

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

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

25. When proteins in solution are heated, the hydrogen bonds in proteins may be broken to result in collapsing of protein secondary structures. What will be the effects of the heating process on ∆H and ∆S of the proteins? (A) ∆H and ∆S all will increase. (B)∆H and ∆S all will decrease. (C) ∆H will increase but ∆S will decrease. (D) ∆H will decrease but ∆S will increase (E)Both ∆H and ∆S will not change. 

1. Look at the picture. What is the teacher holding in her hand? (A) A book. (B) An eraser. (C) A map. (D) A ruler.