13. For the conversion of water to ice at 25℃ and 1 atm,
(A)△G is negative and △H is negative.
(B) △G is negative and △H is positive.
(C) △G is positive and △H is negative.
(D) △G is positive and △H is positive.

9. The MO diagram below is appropriate for B2 (Boron atom), Based on this diagram, B2 (A)has a bond order of one and is diamagnetic. (B) has a bond order of one and is paramagnetic. (C) has a bond order of two and is diamagnetic. (D) has a bond order of two and is paramagnetic.

10. Calculate the work energy, w, gained or lost by the system when a gas expands from 20 L to 35 L against a constant external pressure of 2.0 atm.[1 Lㆍ atm = 101 J] (A)-5.3 kJ (B) -3.0 kJ (C) +3.0 kJ (D) +5.3 kJ

11. When 50.0 mL of 0.400 M Ca(NO3)2 is added to 50.0 mL of 0.800 M NaF, CaF2 precipitates, as shown in the net ionic equation below. The initial temperature of both solutions is 30.00℃. Assuming that the reaction goes to completion, and that the resulting solution has a mass of 100.00 g and a specific heat of 4.18 J/(g ㆍ ℃), calculate the final temperature of the solution. (A)29.45℃ (B) 30.55℃ (C) 31.10℃ (D) 31.65℃

12. Use the given standard enthalpies of formation to calculate AH" for the following reaction (A)-5213.4 kJ (B)-577.2 kJ (C)-47.2 k (D) +47.2 kJ 

14. Each of three identical 15.0-L gas cylinders contains 7.50 mol of gas at 295 K. Cylinder A contains HCN, cylinder B contains NO2, and cylinder C contains O3. According to the kinetic molecular theory, which gas has the highest average kinetic energy? (A)HCN .(B) NO2 (C)O3 (D) All have identical average kinetic energies

15. While mercury is very useful in barometers, mercury vapor is toxic. Given that mercury has a of 59.11 kJ/mol and its normal boiling point is 356.7℃, calculate the vapor pressure in mm Hg at room temperature, 25℃. (A)2.68 x 10-3 mm Hg (B) 2.99 mm Hg (C) 372 mm Hg (D) 753 mm Hg The plots below represent vapor pres assure vs, temperature curves for diethyl ether, ethanol, mercury, and water, not necessarily in that order.

16. Based on the relative strengths of the intermolecular forces of attraction of each substance, which is the most likely vapor pressure vs. temperature curve for diethyl ether? (A)curve (a) (B) curve (b) (C) curve (c) (D) curve (d)

17. How much heat is released when 95.0 g of steam at 100.0℃ is cooled to ice at -15.0℃ ? The enthalpy of vaporization of water is 40.67 kJ/mol, the enthalpy of fusion for water is 6.01 kJ/mol, the molar heat capacity of liquid water is 75.4 J/(mol ．℃ ), and the molar heat capacity of ice is 36.4 J/(mol ．℃ ). (A)54.8 kJ (B) 247 kJ (C) 289 kJ (D) 314 kJ

18. Barium has a radius of 224 pm and crystallizes in a body-centered cubic structure. What is the edge length of the unit cell? (A)259 pm (B) 317 pm (C) 448 pm (D) 517 pm

19. When a particular solid begins to dissolve in water, the temperature rises dramatically. For the dissolving of this solid in pure water (A)(B) (C) (D)