70. To form a buffer solution with pH = 9.0, how many moles of NH4Cl should be added to 3.0 L of 0.20 M NH₃(aq) at 25ºC? (Kb of ammonia = 1.8 × 10^‒5 ; assuming the volume of solution does not change after adding NH₄Cl)
(A) 0.36
(B) 0.72
(C) 1.08
(D) 3.6
(E) None of the above.

66. A 0.20 M solution of MgSO4 has an observed osmotic pressure of 6.0 atm at 25°C. Determine the observed van't Hoff factor for this experiment. (A) 1.23 (B) 2.00 (C) 1.66 (D) 1.80 (E) 1.45

67. Adipic acid contains 49.32% C, 43.84% O, and 6.85% H by mass. What is the empirical formula? (A) C3H5O2 (B) C2HO3 (C) C2H5O4 (D) C3HO3 (E) C3H3O4

68. On a new temperature scale (°L), water boils at 155.00°L and freezes at –10.00°L. Calculate the normal human body temperature using this temperature scale. On the Celsius scale, normal human body temperature is 37.0°C, and water boils at 100.0°C and freezes at 0.0°C. (A) 57.30°L (B) 47.35°L (C) 51.05°L (D) 61.05°L (E) 41.05°L

69. When the following equation C2H5OH + O2⇌ CO2 + H2O is balanced, what are the coefficients? (A) 2, 3, 1, 4 (B) 1, 3, 2, 3 (C) 1, 1, 1, 1 (D) 1, 2, 3, 4 (E) 1, 2, 2, 2

71. Which statement about hydrogen bonding is true? (A) Hydrogen bonding is the intermolecular attractive forces between two hydrogen atoms in solution. (B) The hydrogen bonding capabilities of water molecules cause CH3CH2CH2CH3 to be more soluble in water than CH3OH. (C) Hydrogen bonding of solvent molecules with a solute will not affect the solubility of the solute. (D) Hydrogen bonding interactions between molecules are weaker than the covalent bonds within the molecule. (E) Hydrogen bonding arises from the dipole moment created by the equal sharing of electrons within certain covalent bonds within a molecule.

72. How many effective atoms are there in a body-centered cubic unit cell? (A) 1/2 (B) 1 (C) 2 (D) 3/2 (E) 3

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.