68. A diprotic acid H₂A has K_a1 = 1 x 10^–4 and K_a2 = 1 x 10^–8 . The corresponding base A^2– is titrated with aqueous HCl, both solutions being 0.1 mol/L. Which one of the following diagrams best represents the titration curve which will be seen?
(A)
(B)
(C)
(D)
(E)

64. Select the Lewis structure for XeO2F2 which correctly minimizes formal charges. (A) (B) (C) (D) (E)

65. Which species has the highest bond order? (A) NO+ (B) O2 (C) O2 − (D) O2 2− (E) NO−

66. What hybridization is present in the phosphorus atom in PCl3 and PCl5, respectively? (A) sp 2 , d 2 sp 3 (B) sp 2 , dsp3 (C) dsp, dsp3 (D) sp 3 , d 2 sp 3 (E) sp 3 , dsp3

67. The spectrochemical series is I– < Br– < Cl– < F– < OH– < H2O < NH3 < en < NO2– < CN– . Which of the following complexes will absorb visible radiation of the highest energy? (A) [Co(H2O)6] 3+ (B) [CoI6] 3– (C) [Co(OH)6] 3– (D) [Co(en)3] 3+ (E) [CoCl6] 3– 

69. Which of the following coordination compounds will form a precipitate (AgCl) when treated with an aqueous solution of AgNO3? (A) [Cr(NH3)3Cl3] (B) [Cr(NH3)Cl]SO4 (C) Na3[Cr(CN)6] (D) [Cr(NH3)6]Cl3 (E) None of the above.

70. If a complex ion is square planar, which d-orbital is highest in energy? (A) dx2-y2 (B) dx2 (C) dxy (D) dyz (E) dxz

71. Which of the following statement is incorrect about hydrocarbons? (A) Breaking the C─H bonds separately of CH4 requires different energies. (B) The average C─H bond energy of CH4 is higher than that of H─H. (C) Hydrocarbons are hydrophobic. (D) Longer alkanes are with higher viscosities than shorter ones. (E) Branched alkanes are with lower boiling points than their corresponding straight isomers.

72. Which of the following molecules is an optically active molecule? (A) (B) (C) (D) (E) None of the above.

73. The structure below is the repeating unit of a (A) homopolymer formed by an addition reaction. (B) homopolymer formed by a condensation reaction. (C) copolymer formed by an addition reaction. (D) copolymer formed by a condensation reaction. (E) polyester formed by an addition reaction.

74. Identify the products of the reaction of 3-octene with chlorine. (A) (B) (C) (D) (E)