77. It is desired to determine the concentration of arsenic in a lake sediment sample by means of neutron activation analysis. The nuclide As captures a neutron to form As , which in turn undergoes β decay. The daughter nuclide produces the characteristic γ rays used for the analysis. What is the daughter nuclide?
(A)
(B)
(C)
(D)
(E)

73. Which of the following has a zero dipole moment? (A) NH3 (B) HCN (C) PCl5 (D) SO2 (E) H2O

74. An electron is promoted from the π to the π∗ molecular orbital in an O2 molecule following the absorption of a photon. Compared to the bond length in the non-excited molecule, the O2 bond length will . (A) be shorter (B) be longer (C) not be affected (D) be same (E) None of the above.

75. Determine the percent dissociation of a 0.18 M solution of hypochlorous acid, HClO. The Ka for the acid is 3.5 × 10−8 . (A) 4.4 × 10−2 % (B) 3.5 × 10−6 % (C) 6.3 × 10−9 % (D) 4.4 × 10−4 % (E) 7.9 × 10−3 %

76. The solubility of CaSO4 in pure water at 0 oC is 1.14 gram per liter. The value of the solubility product is . (A) 7.01 × 10–5 (B) 8.37 × 10–3 (C) 7.01 × 10–2 (D) 8.37 × 10–5 (E) None of the above.

複選題78. As shown below, compound IV can be prepared from reagents I, II, and III. Which of the following reaction conditions is the most suitable for the preparation of IV? (A) I is slowly added to II, and III is then added to the above mixture. (B) I is slowly added to II, and the resultant mixture is slowly added to III. (C) II is slowly added to I, and III is then added to the above mixture. (D) II is slowly added to I, and the resultant mixture is slowly added to III. (E) I is slowly added to III, and II is then added to the above mixture.

79. The equilibrium constant of a certain reaction was measured at various temperatures to give the plot shown below. What is Δ S o (J/mol∙K ) for the reaction? (R = 8.314 J/mol∙K ) (A) 0.20 (B) 3.0 (C) −50 (D) −8.3 × 103 (E) 33

80. For the reaction N2(g) + 2H2(g) → N2H4(l), if the percent yield for this reaction is 41.0%, what is the actual mass of hydrazine (N2H4) produced when 30.57 g of nitrogen reacts with 4.45 g of hydrogen? (A) 24.00 g (B) 28.60 g (C) 15.00 g (D) 12.00 g (E) 14.60 g

81. A sample of helium gas has been contaminated with argon gas. At 1 atm and 25°C, the density of the mixture is 0.200 g/L. What is the volume percent helium in the sample? (A) 90.0% (B) 97.5% (C) 80.3% (D) 2.5% (E) 99%

82. Which of the following is NOT a state function? (A) entropy (B) enthalpy (C) internal energy (D) heat (E) temperature

83. A metal ion in a high–spin octahedral complex has four more unpaired electrons than the same ion does in a low–spin octahedral complex. The metal ion could be: (A) V2+ (B) Cu2+ (C) Mn2+ (D) Cr3+ (E) Co2+