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

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

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)

20. The second-order reaction, has a rate constant equal to 3.0 x If the initial concen entration , how long will it take for 90.% of the reactant to disappear? (A)(B) (C) (D)

21. The first-order isomerization reaction: n: cycloprop opane → propene, has a rate constant of . What is the activation energy, Ea, for the reaction? (A)46 klJ/mol (B) 110kJ/mol (C) 260 kJ/mol (D) 380 kj/mol

22. The following figure depicted the variation of A,B,and C concentration variation with reaction time Which equation best represents the reaction? (A)4A(g) → B(g) + 2C(g) (B) 4A(g) + B(g) → 2C(g) (C) 2C(g) → 4A(g) + B(g) (D) 2C(g) + B(g) →4A(g)

23. An equilibrium mixture of CO, O2 and CO2at a certain temperature contains 0.0010 M CO2and 0.0015 M O2. At this temperature, Kc, equals 1.4 x 102 for the reaction: What is the equilibrium concentration of CO? (A)(B) (C) (D)

24. Shown below is a concentration vs. time plot for the reaction2B. For this reaction the value of the equilibrium constant is (A)Kc＜1. (B) Kc-0, (C)kc=1. (D) Kc＞1.