72. Based on MO theory, which molecule is not paramagnetic?
(A) O₂⁻
(B) O₂ ⁺
(C) O₂
(D) N₂
(E) N₂⁺

68. For a reaction involving changes of reactant concentrations ([A]), what is the reaction order (m) when the correlation of ln [A] versus time (t) is a straight line? (A) m=0 (B) m=1/2 (C) m=1 (D) m=2 (E) None of these

69. Consider the reaction Fe3+(aq) + SCN- (aq) FeSCN2+(aq). Which one of the following statements is correct? (A) The equilibrium position shifts to the right after water is added to double the volume (B) The equilibrium position shifts to the right after AgNO3(aq) is added (C) The equilibrium position shifts to the left after NaOH(aq) is added (D) The equilibrium position shifts to the left after Fe(NO)3(aq) is added (E) None of the above is correct

70. Which “P” in the following compounds has the lowest oxidation state? (A) Phosphoric acid (B) Phosphorous acid (C) Hypophosphorous acid (D) Sodium phosphide (E) Black phosphorus

71. How many π electrons are delocalized in 1,4-diphenyl-1,3-butadiene? (A) 4 (B) 8 (C) 16 (D) 24 (E) 32

73. Consider mixing equal volume of 0.1 M Na2CO3 solution and 0.1 M H2SO4 solution. Which statement is correct? (A) [H+ ] is less than 0.05 M (B) [H+ ] is between 0.1 M and 0.05 M (C) [H+ ] is 0.1 M (D) [H+ ] is 0.2 M (E) pH ＞ 7

74. Which is the major specie for a carbonate-containing solution at pH 8.5? (Ka1 = 4.3 × 10–7 , Ka2 = 4.8 × 10–11 for carbonic acid) (A) CO2 (B) H2CO3 (C) HCO3− (D) CO32− (E) C2O42−

75. What is the main contribution for the negative entropy value (ΔSo soln ＜ 0) when formation of LiF(aq) in water? (A) Random dispersal of water (B) Breaking ordered bonding of solids (C) Interaction of Li+ and F− with water molecules (D) Dispersion of Li+ and F− into solution (E) Fast equilibrium

76. The energy required to remove the electron from a hydrogen atom in its ground state is 2.178 × 10–18 J. What is the energy required to excite the electron in the He+ ion from the n = 1 level to the n = 2 level? (A) 1.634 × 10–18 J (B) 2.178 × 10–18 J (C) 3.268 × 10–18 J (D) 8.712 × 10–18 J (E) None of these

77. To increase the value of K for the endothermic reaction as mentioned below, a chemist should__________ . (A) decrease the temperature (B) decrease the container volume (C) increase the total pressure (D) increase the temperature (E) None of these

78. Two moles of an ideal gas undergo isothermal expansion from a volume of 1.0 L to a volume of 10.0 L against a constant external pressure of 1.0 atm. Calculate the changes of internal energy (ΔE). (1 L·atm = 101.3 J) (A) 9.12 × 102 J (B) 1.82 × 103 J (C) –9.12 × 102 J (D) –1.82 × 103 J (E) 0 J