70. The value of the Bohr radius for hydrogen is:
(A)0.529 x 10^-6cm
(B) 0.529 x 10^-8cm
(C) 0.529 x 10^-10cm
(D) 0.529 x 10^-12 cm
(E) 0.529 x 10^-14 cm 

66. The half-life of 14C is 5730 years. A sample taken for radiocarbon dating has been found to contain56 % of its original 14C. Which of the following options is the best estimate for the age of the sample? (Radioactive decay of 14C follows first-order kinetics.) (A)4.8x102(B) 4.8x103(C) 4.8x 105(D) 4.8 x 106(E) 4.8 x 100

67. Sort the molecules in the order from the largest bond angle to the smallest bond angle: H2O, NH3, BF3, CH4, CO2 (A) CH4, CO2, H2O, BF3, NH3 (B) CO2, BF3, CH4, NH3,H2O (C) NH3, H2O, BF3, CO2, CH4 (D) H2O, NH3, BF3, CH4, CO2 (E) BF3, NH3,  H2O, CH4, CO2

68. If the ionization energy of a hydrogen atom is 13.6 eV, the energy required to excite it from ground state to the next higher state is approximately: (A) 3.4eV(B)10.2eV(C)17.2eV(D)13.6eV(E)6.8 ev

69. Hemocyanins (Hc) are proteins that transport oxygen throughout the bodies of some invertebrate animals. These metalloproteins contain two copper atoms that reversibly bind a single oxygen molecule (O2). The scheme below shows a proposed structure of how the copper atoms bind to oxygen. What is the oxidation state of the copper atoms in the product? L is a neutral ligand.   (A)+1,+1(B)+2,+2(C)+3,+3(D)+0.5.0.5(E)+1.5.+1.5

71 . Select the rate law that corresponds to the data shown for the following reaction: A+B→ Products [X]0 represents the initial concentration for a species X.(A) Rate = k[A]3 (B) Rate = k[A]2[B]1 (C) Rate = k[A]1[B]2 (D) Rate = k[B]3 (E) None of the above

72. Which one of the following tetrahedral MXF- complexes has the strongest crystal field stabilization? (A) FeCl42- (B) MnCl42- (C) CoCl42- (D) NiCI42- (E) CuCI42- 

73. Although the peroxide ion, O22-, and the acetylide ion. C22-, have long been known. the diazenide ion N22- has only been prepared in 2001. By comparison with the other diatomic species, N2 and O2, what is the bond order and number of unpaired electrons for N22-, respectively? (A)1,1 (B)3.1 (C)2.1 (D)2.0 (E) 2.2

74. Calculate the reduced mass of HF molecule given that the mass of H atom is 1 amu and the mass of F atom is 19 amu. Note: assume 1 amu = 20 mg. (A) 18mg (B) 19mg (C) 20mg (D) 21 mg (E) 22 mg 

75. What factors affect the ionization energy of an atom? (A) Electron shielding (B) Electron configuration (C) Nuclear charge (D) All of the above (E) None of the above

76. How can we explain the fact that CCl4 is a liquid and CL. is a solid at 25℃? Which of the following options is the best explanation? (A) CCl4 has a larger dipole moment than Cl4 due to the higher electronegativity of CI compared to I. (B) Cl4 has a larger dipole moment than CCl4 because there is stronger electron repulsion in the Cl-I bonds than in the C-CI bonds. (C) London dispersion forces are stronger in C Cl4 than in  Cl4 because Cl is more electronegative than I. (D) London dispersion forces are stronger in  Cl4 than in C Cl4 because  Cl4 has a more easily polarizable electron cloud. (E) None of the above.