CHM 2046 Test 2 Review: Chapter 12, Chapter 13, & Chapter 14

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1 Chapter 12: 1. In an 80.0 L home aquarium, the total pressure is 1 atm and the mole fraction of nitrogen is Henry s law constant for N 2 in water at 25 is 6.1 x What mass of nitrogen is dissolved at 25? a. 2.5 g b. 1.1 g c g d. 5.3 g e. 4.7 g 2. Which of the following would produce the highest vapor pressure in water? a moles of NaC 2 H 3 O 2 b mole of KMnO 4 c moles of Al 2 O 3 d mole of Li 2 SO 4 e moles of NH 4 Cl 3. The vapor pressure of pure water at 25 is 23.8 torr.what is the vapor pressure at 25 of an aqueous solution that is 5.50% NaCl by mass? a torr b torr c torr d torr e torr 4. An aqueous solution containing 35.9 g of an unknown molecular (nonelectrolyte) compound in g of water was found to have a freezing point of 1.3. The k f of water is 1.86 /m. What is the molar mass of the unknown compound? a g/mol b g/mol c g/mol d g/mol e g/mol 5. An aqueous solution contains 25.0 g of CaCl 2 and ml of water. What is the boiling point of this solution? The k b of water is /m.

2 a b c d e What mass of sucrose (C 12 H 22 O 11 ) should be combined with 5.00 x 10 2 g of water to make a solution with an osmotic pressure of 8.55 atm at 298 K? Assume a density of 1.00 g/ml for the solution. a g b g c g d g e g Chapter 13: 7. Consider the following reaction: 2 HBr ( g ) H 2 ( g ) + Br 2 ( g ) In the first 15.0 s of this reaction, the concentration of HBr dropped from M to M. What is the average rate of the reaction in this time interval? a. 1.5 x 10 3 M/s b. 1.5 M/s c. 5.1 x 10 3 M/s d. 2.1 x 10 3 M/s e. 2.1 M/s 8. Consider the following reaction and the data below: 2 NO 2 ( g ) + F 2 ( g ) 2 NO 2 F ( g ) [NO 2 ] (M) [F 2 ] (M) Initial Rate (M/s)

3 What is the overall order of the reaction? a. second order b. first order c. zero order d. ½ order e. ¾ order 9. Which of the following would indicate a second order reaction? a. A plot of the concentration of the reactant versus time yields a straight line b. The reaction has a half life that is independent of the initial concentration c. The reaction has a half life that gets shorter as the initial concentration is increased d. A plot of the natural log of the concentration of the reactant versus time yields a straight line e. None of the above 10. The following reaction was monitored as a function of time: AB A + B A plot of ln [AB] versus time yields a straight line with slope /s. What is the value of the rate constant for this reaction at this temperature? a. 4.5 M 1 s 1 b. 4.5 x 10 3 M s 1 c. 4.5 x 10 3 s 1 d. 4.5 x 10 2 s 1 e. 4.5 M 1 s The decomposition of SO 2 Cl 2 is first order in SO 2 Cl 2 and has a rate constant of 1.42 x 10 4 s 1 at a certain temperature. If the initial concentration of SO 2 Cl 2 is M, what is the concentration of SO 2 Cl 2 after 200 s? a M b M c M d M e M

4 12. The half life for the radioactive decay of U 238 is 4.5 billion years and is independent of initial concentration. How long will it take for 10% of the U 238 atoms in a sample of U 238 to decay? a. 6.8 x 10 8 years b. 3.4 x 10 5 years c. 34 x 10 8 years d. 68,000 years e. 6.8 x 10 7 years 13. A reaction has a rate constant of /s at 400 K and 0.689/s at 450 K. What is the activation barrier for the reaction? a. 156 kj/mol b. 143 kj/mol c. 143 J/mol d. 122 J/mol e. 122 kj/mol 14. Consider the following mechanism: AB + AB AB 2 + A k 1 AB 2 + C AB + BC Slow Fast k 2 What is the rate law for the reaction that is represented by the mechanism above? a. rate = k 1 [AB] b. rate = k 1 [AB] 2 [AB 2 ] [A] c. rate = k 1 k 2 [AB] 2 [AB 2 ] [C] d. rate = k 2 [AB 2 ] [C] [AB] [BC] e. rate = k 1 [AB] 2 Consider the following three step mechanism for questions 15 and 16. k 1 Cl 2 ( g ) 2 Cl ( g ) Fast k 2 Cl ( g ) + CHCl 3 ( g ) HCl ( g ) + CCl 3 ( g ) Slow k 3 Cl ( g ) + CCl 3 ( g ) CCl 4 ( g ) Fast

5 k What is/are the intermediate(s) in the mechanism above? a. Cl b. Cl and Cl 2 c. Cl 2 d. CCl 3 e. Cl and CCl What is the predicted rate law of the mechanism above? a. rate = k 3 [Cl] [CH 3 Cl] b. rate = k 4 [Cl] [CCl 3 ] c. rate = k 1 [Cl 2 ] d. rate = k [Cl] [CHCl 3 ] 1/2 e. rate = k [Cl] ½ [CHCl 3 ] Chapter 14: 17. What is the equilibrium constant expression for the chemical equation below? NH 4 HS ( s ) NH 3 ( g ) + H 2 S ( g ) [NH4HS] a. [NH 3] [H2S] [NH 3] [H2 S] b. [NH HS] 4 c. [NH 4 HS] d. [NH 3 ] [H 2 S] e. [NH 4 HS] [NH 3 ] [H 2 S] 18. The reaction below has an equilibrium constant of Kp = 2.26 x 10 4 at 298 K. CO ( g ) + 2 H 2 ( g ) CH 3 OH ( g ) What is the Kp for the following reaction at 298 K? 2 CH 3 OH ( g ) 2 CO ( g ) + 4 H 2 ( g ) a x 10 9 b x 10 9 c x 10 5 d x 10 5 e x 10 5

6 19. Consider the following reactions and their respective equilibrium constants: NO (g) + ½ Br 2 ( g) NOBr ( g) Kp = NO (g) N 2 ( g) + O 2 ( g) Kp = 2.1 x What is the equilibrium constant for the following reaction? N 2 ( g) + O 2 ( g) + Br 2 ( g) 2 NOBr ( g) Kp =? a. 2.5 x b. 2.5 x c. 1.3 x d. 1.3 x e. 1.8 x Consider the following reaction: CO ( g ) + 2 H 2 ( g ) CH 3 OH ( g ) An equilibrium mixture of this reaction at a certain temperature was found to have [CO] = M, [H 2 ] = M, and [CH 3 OH] = M. What is the value of Kc at this temperature? a x 10 2 b x 10 2 c x 10 4 d x 10 4 e x Consider the following reaction: H 2 ( g) + I 2 ( g) 2 HI ( g) A reaction mixture in a 3.67 L flask at a certain temperature initially contains g H 2 and 96.9 g I 2. At equilibrium, the flask contains 90.4 g HI. What is the Kc for the reaction at this temperature? a. 764 b. 647 c x 10 4 d x 10 4 e x What is the Kp for the following reaction at 298 K? N 2 (g) + 3 H 2 (g) 2 NH 3 (g) Kc = 3.7 x 10 8 a x 10 5 b x 10 5 c x 10 5

7 d x 10 6 e x For the following reaction Kc = at 500 K. N 2 O 4 (g) 2 NO 2 (g) If a reaction vessel initially contains an N 2 O 4 concentration of M at 500 K, what are the equilibrium concentrations of N 2 O 4 and NO 2 at 500 K? a. [N 2 O 4 ] = M, [NO 2 ] = M b. [N 2 O 4 ] = M, [NO 2 ] = M c. [N 2 O 4 ] = M, [NO 2 ] = M d. [N 2 O 4 ] = M, [NO 2 ] = M e. [N 2 O 4 ] = M, [NO 2 ] = M *Use the following chemical reaction to answer questions * C (s) + CO 2 (g) 2 CO (g) Kp = 1.2 x 10 3 ΔH = kj/mol 24. If the reaction is at equilibrium and 10.0 g of C (s) is added, which of the following will occur? a. the reaction will shift left b. the reaction will shift right c. the reaction will not shift; it s at equilibrium d. none of the above 25. If the reaction is at equilibrium and the volume of the container decreases by 0.05 L, which of the following will occur? a. the reaction will shift left b. the reaction will shift right c. the reaction will not shift; it s at equilibrium d. none of the above 26. If the reaction is at equilibrium and heat is added, which of the following will occur? a. the reaction will shift left b. the reaction will shift right c. the reaction will not shift; it s at equilibrium d. none of the above

8 27. If a reaction vessel contains a partial pressure of CO 2 at 0.50 atm and a partial pressure of CO at 2.5 atm, which of the following will occur? a. the reaction will shift left b. the reaction will shift right c. the reaction will not shift; it s at equilibrium d. none of the above Answer Key: 1. B 2. B 3. C 4. E 5. B 6. E 7. A 8. A 9. C 10. C 11. A 12. A 13. E 14. E 15. E 16. E 17. D 18. B 19. D 20. A 21. A 22. E 23. C 24. C 25. A 26. B 27. B

CHEM 1412 Practice Exam 1 - Chapters Zumdahl

CHEM 1412 Practice Exam 1 - Chapters 11 13 Zumdahl Some equations and constants: T = Km P = XP = MRT ln[a]t = kt + ln[a]o 1 / [A]t = kt + 1 / [A]o t1/2 = ln(2) / k t1/2 = 1 / k{a]o Kp = Kc(RT) n ln(k1/k2)