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⁺

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

84. Which of the following coordination compounds will form a precipitate when treated with an aqueous solution of AgNO3? (A) [Cr(NH3)3Br3] (B) [Mo(Cl)2(NH3)4](NO3) (C) Na3[WCl6] (D) [Pt(NOlinear)2(OAc)2](Br)2 (E) None of the above.

85. Which of the following species is diamagnetic? (A) CN (B) B2 (C) O2 (D) All of the above. (E) None of the above.

86. Which of the lines in the figure below is the best representation of the relationship between the volume of a gas and its pressure, other factors remaining constant? (A) a (B) b (C) c (D) d (E) e

87. Sulfur tetrafluoride adopts a see-saw geometry with two axial F atoms with a F–S–F angle of about 180º and two equatorial F atoms at about 90º from the axial fluorines. Which statement most accurately describes the axial and equatorial S–F bonds? (A) The axial S–F bonds are longer because the two fluorine atoms must share bonding to the same orbital on sulfur. (B) The axial S–F bonds are longer because they experience greater repulsion from the other fluorine atoms in the molecule. (C) The equatorial S–F bonds are longer because the equatorial F–S–F bond angle is the smallest in the molecule. (D) The equatorial S–F bonds are longer because they experience greater repulsion from the lone pair on sulfur. (E) The equatorial S–F bonds are longer because they experience greater repulsion from two axial fluorine atoms.

88. According to the Haber-Bosch process, which statement is true? (A) The reaction to produce NH3 from H2 and N2 is reversible. (B) According to the Le Châtelier’s principle, the overall reaction is favorable to produce products in the state of high pressure. (C) Increasing the reaction temperature can accelerate the reaction to equilibrium. (D) Using Fe as a catalyst can accelerate the reaction to equilibrium, but cannot change the equilibrium between the reagents and products. (E) All statement are true.

89. A sample of a washing powder that contains a mixture of Na2CO3 and NaHCO3 is titrated with aqueous HCl and the following result is obtained: What is the mole ratio of CO32– to HCO3– in the washing powder? (A) 2 mole CO32– : 1 mole HCO3– (B) 1 mole CO32– : 1 mole HCO3– (C) 1 mole CO32– : 2 mole HCO3– (D) 1 mole CO32– : 3 mole HCO3– (E) 3 mole CO32– : 1 mole HCO3–(一律送分)