83. Sort the following compounds in decreasing order by their pKa valuesCfrom highest to lowest).
(A) I＞Ⅱ＞Ⅲ＞Ⅳ
(B) IV＞Ⅲ＞Ⅱ＞I
(C)IV＞Ⅱ＞Ⅲ＞I 
(D)Ⅲ＞I＞Ⅱ＞IV
(E)I＞Ⅲ＞Ⅱ＞I

79. At a particular temperature, the half-life of a zero-order reaction is 29.0 min. How long will it take for the reactant concentration to deplete to 1/8 of the initial concentration? (A) 87.0 min (B) 58.0 min (C) 50.8 min (D) 232 min (E) 203 min

80. The reaction, 2H2O(g) — 2H2(g) + O2(g), has a positive value for △G°. Which of tfie following statements must be true? (A) The reaction is slow. (B) The reaction will not occur. That is, when H2O(g) is introduced into a flask, no O2 or H2 will fonn even over a long period of time. (C) The equilibrium lies far to the right. (D) The reaction is exothermic. (E) None of these are true.

81. Why does the pH value afiect the separation of amino acids by electrophoresis? Please choose tiie wrong reason. (A) Amino acids exist as zwitterions. (B) At low pH values, the amino acid molecules will be strongly attracted to the negative electrode. (C) At high pH values, the amino add molecules will be strongly attracted to the negative electrode. (D) In basic solution, the net chaise is negative due to die dissociation of the carboxylic acid groups. (E) None of the above.

82. What is a virtual state in Raman spectroscopy? Please choose the correct description. (A) It helps us to visualize both elastic and inelastic scattering processes. (B) It lies between the ground state and a vibrational state of tfie molecule. (C) It is also a first vibrational state. (D) It is a real electronic energy state. (E) None of die above.

84. Which of the reactions below shows the correct usage of curly arrows? (A)(B)(C)(D)(E)

85. Which of the following radicals is the most stable? (A)(B)(C)(D)(E)

86. Disulfide linkages can form between________ . (A) two cysteine residues (B) two methionine residues (C) a cysteine residue and a methionine residue (D) two ttireonine residues (E) a methionine residue and a flireonine residue

87. What is the electron configuration for the barium atom? (A) 1s22s22p63p64s2 (B) 1s22s22p63s23p64s1 (C) 1s22s22p63s23p63d104s2(D) [Xe] 6s2 (E) 1 s22s22p63s2

88. Choose the correct statement. (A) A reaction that exhibits a negative value of △S cannot be spontaneous. (B) Exothermic reactions are always spontaneous. (C) Free energy is independent of temperature, (D) At constant pressure and temperature, a decrease in free energy ensures an increase in the entropy of the system. (E) None of the above.

89. Which of the following statements is true about the ionization energy ofMg+? (A) It will be equal to the negative value of the electron affinity ofMg. (B) It will be equal to the negative value of the electron aflfinity of Mg+・ (C) It will be equal to the ionization energy of Li. (D) It will be equal to the negative value of the electron affinity of Mg2+. (E) None of the above.