76. An unknown compound is cooled at 1 atm, and it freezes at 50.0 K to form Solid I. At a lower temperature, Solid I rearranges to Solid II, which has a different crystal structure. Thermal measurements show that ΔH an ΔS for the I → II phase transition are –700.0 J/mol and –20.0 J/K mol, respectively. What is the temperature of Solids I and II in equilibrium?
(A) 13.6 K
(B) 19.8 K
(C) 35.0 K
(D) 59.8 K
(E) 98.2 K

72. Which of the following statements is correct? (A) Arrhenius postulated that an acid is a proton (H+) donor, and a base is a proton acceptor. (B) A buffer with a large capacity contains large volumes of the buffering components. (C) For the titrations of weak acids with strong bases, the greater pH value at the equivalence point is obtained when the stronger acid is used. (D) For a particular buffering system, all solutions that have the same ratio of [A– ]/[HA] have the same pH value. (E) An acid-base indicator can be used to determine the equivalence point of an acid-base titration because of its ability to mark the half-equivalence point of a titration by changing color.

73. At a certain temperature, placing one mole of ammonia gas into a sealed container results in 40% ammonia decomposition at equilibrium. What is the equilibrium constant KC for ammonia decomposition at that temperature? (ammonia decomposition: 2NH3(g) → N2(g) + 3H2(g)) (A) 0.043 (B) 0.12 (C) 0.80 (D) 8.33 (E) 17

74. Complete the Lewis structure for the molecular formula (C5H7ON) below. This molecule has _____ single bonds, _____ multiple bonds and ____ sp2 hybridized atoms. (A) 4, 2, 2 (B) 4, 2, 4 (C) 11, 2, 2 (D) 11, 2, 4 (E) 11, 5, 4

75. A product is electroplated by copper from CuSO4 solution. A constant current of 9.65 amp is applied by an external power supply. How long will it take to deposit 6.35 × 102 g of Cu onto the surface of product? (Cu = 63.5 g/mol) (1F = 96485 C/mol) (A) 14.22 s (B) 8.9 min (C) 2.54 h (D) 55.5 h (E) 1.37 days

77. What are the signs (+, –, or 0) of ΔH, ΔS, and ΔG for the spontaneous vaporization of a liquid to a vapor? (A) (ΔH, ΔS, ΔG) = (+, +, +) (B) (ΔH, ΔS, ΔG) = (+, –, +) (C) (ΔH, ΔS, ΔG) = (0, 0, 0) (D) (ΔH, ΔS, ΔG) = (+, +, –) (E) (ΔH, ΔS, ΔG) = (–, – , –)

78. The reduction potentials for Au3+ and Cr3+ are as follows: (A) –7.37 × 102 kJ (B) –5.79 ×102 kJ (C) –1.6 × 102 kJ (D) 7.37 × 102 kJ (E) 10 × 102 kJ

79. How many different structures do SeCl4, CBr4, KrF4, CH4, and TeF4 have? (A) 1 (B) 2 (C) 3 (D) 4 (E) 5

80. A weak acid HA is dissolved in enough water to prepare an acidic solution. The pH value and osmotic pressure of resulting solution at 27o C are 6 and 0.246 atm, respectively. What is the Ka of HA? (R = 0.082 L· atm/K·mol； assuming Van’t Hoff factor = 1) (A) 1.00 × 10–10 (B) 2.30 × 10–10 (C) 1.10 × 10–9 (D) 6.10 × 10–9 (E) 5.80 × 10–8

81. The pH of a bottle of vinegar is 2.75 at 25℃. What is the mass percentage concentration (w/w) of acetic acid in this vinegar, assuming no other acid is presented? (Ka of acetic acid: 1.8x10-5； pKa of acetic acid: 4.74； 10-2.75 = 0.0018； 102.75 = 562.3； assuming the density of vinegar = 1 g/cm3 ； CH3COOH=60 g/mol) (A) 5.0% (B) 4.0% (C) 3.0% (D) 2.0% (E) 1.0%

82. Which of the following complexes can exhibit optical isomerism? (en = H2N–CH2–CH2–NH2) (A) cis–Co(NH3)4Cl2 (B) trans–Co(en)2Br2 (C) cis–Co(en)2Cl2 (D) Co(NH3)3Cl3 (E) none of these