25. Which of the following compounds is the strongest acid?
(A) Acetic acid
(B) Chloric acid
(C) Hypochlorous acid
(D) Boric acid
(E) Chlorous acid

21. Below is a phase diagram for compound X. You wish to purify a sample of X that was collected at P = 1.0 atm and T = 100 by subliming it. In order to sublime the sample, you should (A) increase P to 1.5 atm and then increase T'to 300 K. (B) increase T to 300 K, keeping P = 1.0 atm. (C) lower P to 0.5 atm and then increase T to 200 K. (D) increase T to 300 K and then lower P to 0.5 atm. (E) abandon the attempt to sublime X.

22. Alkali halides commonly have either the sodium chloride structure or the cesium chloride structure. The molar mass of CsCl is 2.88 times the molar mass of NaCl, and the edge length of the unit cell for NaCl is 1.37 times the edge length of the CsCl unit cell. Determine the ratio of the density of CsCl to the density of NaCl. (A) 0.541 (B) 0.984 (C) 1.02 (D) 1.85 (E) 2.10

23. Liquid A has vapor pressure x. Liquid B has vapor pressure y, and x>y.What is the mole fraction of A in the liquid mixture if the vapor above the solution is 30% A? (A)0.3y/(0.7x+0.3y) (B) 0.7y/(0.3x+0.7y) (C) 0.3x/(0.3.xc+0.7y) (D)0.7x/(0.7x+0.3y) (E) none of these

24. The oxidation states of P in KPF6 is: (A)+1 (B)+3 (C)+5 (D)-3 (E) -5

26. Which of the following ions has the lowest standard reduction potential? (A) Ag+ (B) Fe3+(C) Cr3+ (D) Mg2+  (E) Al3+

27. Which of the following names of ions is incorrect? (A) stannous: Sn2+ (B) plumbous: Pb2+ (C) ferric: Fe2+ (D) nitrate: NO3- (E) dichromate: Cr2O72-

28. The density of compound XHn as gas is 2.393 times that of O2. If 0.01 mol of this compound reacts with excess O2, 0.36 g of water is generated. The atomic weight of element X is: (A) 69.72 g/mol (B) 72.55 g/mol (C) 74.92 g/mol (D) 78.97 g/mol (E) 83.80 g/mol

29. Which of the following compound can be dissolved in water easily? (A) CsCl (B) AgCl (C) BaSO4 (D) CaF2 (E) MgCO3

30. Which of the following statements is correct? (A) NaF: acidic, cation acts as an acid )(B)NH4CI: neutral, cation acts as an acid, and anion acts as (C) KCN: basic, cation is from strong base； anion is from strong acid (D) AI(NO3)3: neutral, cation is from strong base； anion is from strong acid (E) FeCl3: acidic, hydrated cation acts as an acid

31. Which of the following statements is correct for a mercury cell to produce chlorine and sodium hydroxide? (A) a reduction reaction occurs at anode to generate (1) (B)(1) is H2 (C) (2) is pure Hg (D) (3) is NaOH solution (E) (4) is water vapor