72. A certain drug is metabolized in the human body following second-order kinetics, with the rate law given by: Rate= k [D]²
where [D] is the concentration of the drug in mg/L, and k is the rate constant in L·. At
time t=0, the drug concentration in the bloodstream is 20.0 mg/L. After 30.0 min, the
concentration drops to 10.0 mg/L.
How long will it take for the concentration to drop to 5.0 mg/L?
(A) 60.0 min
(B) 45.0 min
(C) 37.5 min
(D) 90.0 min
(E) 120.0 min

68. Which of the following statements is incorrect?(A) An orbital can accommodate at most two electrons with the same spin quantum number.(B) The electron density at a point is disproportional to Ψ2 at that point.(C) The quantum number of an electron must be either + .(D) A 2p orbital is more penetrating than a 2s; i.e., it has a higher electron density near thenucleus and inside the charge cloud of a 1s orbital.(E) All of these are incorrect.

69. The solubility of the ionic compound M2X3, having a molar mass of 288 g/mol, is 3.60× g/Lat 25oC. What is the Ksp of the compound at 25℃?(A)(B) (C) (D) (E)

70. What is the pH of a 0.01 M MA solution where MA is a salt that fully dissociates into M⁺ and Ain water? The acid dissociation constant (Ka) for its conjugate acid HA is 1.0×(A) 5 (B) 6 (C) 7 (D) 8 (E) 9

71. What is the equilibrium concentration of HA²- in a 1 M H3A solution with the followingdissociation constants?(A)(B) (C)(D)(E)

73. The balanced equation for the reaction of the gases nitrogen dioxide and fluorine is If the first step is the rate-determining step, which of the following expressions correctlyrepresents the rate law?(A) Rate= k [NO2]2[F2] (B) Rate= k [NO2][F2] (C) Rate= k2 [NO2][F](D) Rate= k1 [NO2][F2] (E) None of the above.

74. Consider the ammonia synthesis reaction: where △G° = -31.3 kJ/mol of N2 consumed at 25°CWhich of the following statements correctly predicts the direction of the reaction when =1.00 atm?(A) the system moves to the right(B) the system moves to the left(C) the system is already at equilibrium(D) the system moves to the left if the temperature increases(E) not enough information

75. What is the solubility of solid CaF2 in a 0.10 M NaF solution?(A)(B)(C)(D)(E)

76. fn a real gas system, the van der Waals equation is used to consider gas behaviors. van der Waals equation is written as: [P + a(n2/V2)](V - nb)=nRTWhich of the kinetic molecular theory postulates is incorrect in a real gas system so that thecorrection factor of pressure is required? P=observed pressure, T=temperature, V=volume of the container, n=mole of the gas, a and b=van der Waals constants, and R=Avogadro constant. a(n2/V2)=correction factor of pressure compared to the ideal gas law.(A) The particles in a gas are in constant, random motion.(B) The combined volume of the particles is negligible.(C) The particles exert no forces on one another.(D) Any collisions between the particles are completely elastic.(E) The average kinetic energy of the particles is proportional to the temperature in Kelvins.

77. Three electrochemical cells were connected in series so that the same quantity of electrical current passes through all three cells. fn the first cell, 1.15 g of chromium metal was deposited from a chromium(III) nitrate (Cr(NO3)3) solution. fn the second cell, 6.31 g of osmium was deposited from a solution made of Osn+ and nitrate ions.Choose the correct name of the salt. Cr=52.0 g/mol; Os=192.2 g/mol(A) osmium(II) nitrate (B) osmium(III) nitrate (C) osmium(IV) nitrate(D) osmium(V) nitrate (E) osmium(VI) nitrate

78. A pain relief medication indicates that every 6 g of powder contains approximately 480 mg of ibuprofen. Assuming all of the active ingredients are ibuprofen, the powder is fully dissolved in 0.5 L of isopropanol. What is the approximate concentration of ibuprofen in the resulting solution in ppm? (The density of isopropanol is 0.79 g/cm3.)(A) 0.12 ppm (B) 480 ppm (C) 960 ppm (D) 1215 ppm (E) 1304 ppm