Chemistry 106 Fall 2006 Exam 2 Form A · PDF fileChemistry 106 Fall 2006 Exam 2 Form A 6....

Chemistry 106 Fall 2006 Exam 2 Form A

1. When 5.000 grams of RbClO4 are dissolved in 25.00 g of water, the temperature drops

from 25.00ºC initially to 14.53ºC. What is ΔHsoln for RbClO4? Heat capacity of water is

C(H2O) = 4.184 J•g-1•˚C-1.

A. 0.2190 kJ/mol B. -10.96 kJ/molC. -40.50 kJ/mol D. 10.96 kJ/molE. 40.50 kJ/mol

2. Which of the following will have a heat of hydration that is greater than Na+?

A. Rb+ B. Be2+ C. I- D. Cu+ E. K+

3. The sign and magnitude of ΔHsoln depends on

A. solvent-solvent intermolecular forces.B. solute-solvent intermolecular forces.C. solute-solute intermolecular forces.D. all the above.

4. According to the second law of thermodynamics, the change in the entropy of the universe(ΔSuniv) during a spontaneous reaction is

A. negative.B. zero.C. less than the change in entropy of the system (ΔSsys).D. randomE. positive.

5. Determine ΔSrxn for

H2 (g) + I2(g) 2HI (g)given

Substance S∫ (J/mol K)

H2 (g) 130.58 I2 (g) 116.73 HI (g) 206.3

A. -165.29 J/K mol B. 398.75 J/K molC. 165.29 J/K mol D. -41.10 J/K molE. 206.3 J/K mol


6. Processes with __________ are always spontaneous.

A. ΔH > 0 and ΔS > 0B. ΔH > 0 and ΔS < 0C. ΔH < 0 and ΔS < 0D. ΔH < 0 and ΔS > 0E. All of the above

7. Hydrogen reacts with nitrogen to form ammonia (NH3) according to the reaction

3H2 (g) + N2 (g) 2NH3 (g)

The value of ΔHº is -92.38 kJ/mol and ΔSº is -198.2 J/K mol. Determine ΔGº at 298 K.

A. 105.8 kJ/molB. 5.897 × 104 kJ/molC. -16.66 kJ/molD. 297.8 kJ/molE. -33.32 kJ/mol

8. Which of the following processes will lead to a positive change in entropy of the system?

A. Sodium chloride crystals form as salt water evaporates.B. Stalactites form in a cave.C. Helium gas escapes from the hole in a balloon.D. A model airplane is put together.E. None of the above

9. Which of the following will have the greatest standard molar entropy (Sº)?

A. He (g) B. H2O(l ) C. NH3 (g) D. NaCl(s)E. C (s, graphite)


10. What is the maximum amount of work (∆GoRXN) that can be done by the reaction:

CH4 (g) + 2 O2 (g) CO2 (g) + 2H2O(g)

given

Substance ΔGºf (kJ/mol)

CH4 (g) -50.8

CO2 (g) -394.4

H2O (g) - 228.57

A. Not enough information is provided to answer this question.B. -50.8 kJ/molC. -749.9 kJ/molD. 572.1 kJ/molE. -800.7 kJ/mol

11. The formation of triglycerides from fatty acids and glycerol produces __________ inaddition to the triglyceride:

A. an acid (H+) B. water (H2O)C. methane (CH4) D. ammonia (NH3)E. none of the above


12. Which of the following compounds is not an α-amino acid?

A. B.

C. D.

E. None are α-amino acids


13. Which of the following molecules contains one or more chiral centers? In other words: whichmolecules have enantiomers?

A. B. H2CClBr

C. D.

E. All of the above

14. A two tablespoon (35 g) serving of peanut butter contains 12 g of fat and a total of 140Calories. Calculate the number of Calories from fat in the serving. Assume fat has a fuel valueof 38 kJ/g (1 Cal = 4.184 kJ).

A. 65 Calories B. 9 CaloriesC. 109 Calories D. 456 CaloriesE. 33 Calories

15. The fifth step in the catabolism of glucose is the reaction:

C3H2O2(OPO3)24 - + H2O ––––> C3H2O4HOPO32 - + HPO42- ∆G = ?

Simultaneously the body uses the HPO42- ion in the following reaction:

ADP + HPO42- ––––> ATP + H2O ∆G = 30.5 kJ

Which statement about the process is true?

A. The ∆G > 0 for the first reaction and the overall process is spontaneous.B. The ∆G = -30.5 kJ for the first reaction and the overall process is spontaneous.C. The ∆G < 0 for the first reaction and the overall process is spontaneous.D. The ∆G > 0 for the first reaction and the overall process is nonspontaneous.E. The ∆G < 0 for the first reaction and the overall process is nonspontaneous.

16. The subunits of the backbone of DNA are:

A. carboxylic acidsB. peptidesC. sugarsD. fatty acidsE. amines


17. The rate of disappearance of HI in the reaction 2 HI (g) → I2 (g) + H2 (g) is shown in the

figure below. What is the instantaneous rate of this reaction at t = 5 sec?

A. -0.025 M/s B. -0.005 M/sC. -0.100 M/s D. -0.010 M/sE. -0.125 M/s

18. Indicate which of the following compounds is not a component of photochemical smog:

A. NO2 B. NOC. H2O D. O3E. they all are components of smog

19. For the reaction 2CH3CH3(g) + 7O2(g) ---> 4CO2(g) + 6H2O(g)which expression correctly indicates the relation between the rates of change of CH3CH3concentratin and H2O concentration?

A. -3∆[CH3CH3]/∆t = ∆[H2O]/∆tB. ∆[CH3CH3]/∆t = 6∆[H2O]/∆tC. -∆[CH3CH3]/∆t = ∆[H2O]/∆tD. -6∆[CH3CH3]/∆t = ∆[H2O]/∆tE. -∆[CH3CH3]/∆t = 4∆[H2O]/∆t


20. HI dissociates to form I2 and H2:

2 HI (g) → H2 (g) + I2 (g).

If the concentration of HI changes at a rate of -0.45 M/s, what is the rate of appearance ofI2 (g)?

A. 0.90 M/s B. -0.23 M/sC. 0.23 M/s D. -0.45 M/sE. 0.45 M/s

21. In the combustion of methane

CH4 (g) + 2 O2 (g) → CO2 (g) + 2 H2O (g)

which reactant has the greatest rate of disappearance?

A. O2 B. CH4C. CO2 D. H2OE. All disappear at the same rate

22. The reaction

A + 2B → C

is first order in B and second order in a. The overall order of the reaction is

A. 3rd. B. 2nd. C. 1st. D. 0th. E. 4th.

23. The reaction 2 NO (g) + O2 (g) → 2 NO2 (g) has the rate law Rate = k[O2][NO]2. If the

concentration of NO is reduced by a factor of two, the rate will

A. double.B. be reduced by a factor of 4.C. be increased by a factor of 4D. remain the same.E. be reduced by a factor of 2.


24. Which of the following plots indicates the reaction is second order?

A. B.

C. D.

E. All of the above could be second order.

25. What are the units of the rate constant for a first-order reaction?

A. M/s B. 1/(Ms) C. 1/(Ms2) D. 1/(M2s) E. 1/s

26. The first order reaction A → B, has k = 5.67 s-1. If [A]0 = 0.500 M, how long will it take

[A] = 0.124 M?

A. 8.18 s B. 0.246 s C. 0.488 s D. 0.123 s E. 0.100 s

27. Determine the overall order of the reaction: H2 (g) + 2 ICl (g) → I2 (g) + 2 HCl (g)

from the following data (remember P, pressure, is proportional to concentration):

Experiment [H2] (torr) [ICl] (torr) Rate (torr/s)

1 250 325 1.34 2 250 81 0.331 3 50 325 0.266

A. 4th B. 3rd C. 1st D. 2nd E. 0th


28. Given the following data, determine the rate constant, k, of the reaction:

H2 (g) + 2 ICl (g) → I2 (g) + 2 HCl (g):

Experiment [H2] (torr) [ICl] (torr) Rate (torr/s)

1 250 325 1.34 2 250 81 0.331 3 50 325 0.266

A. 6.06 × 104 torr-1s-1 B. 1.65 × 10-5 torr-1s-1

C. 8.17 × 10-5 torr-1s-1 D. 1.34 torr-1s-1

E. 3.03 × 10-5 torr-1s-1


Energy profiles for four different reactions

29. Which of the reactions will have the largest rate constant?

A. III B. IV C. II D. I E. All the same

30. The reaction NO2 (g) + CO (g) → NO (g) + CO2 (g) is thought to occur by the following

mechanism:

Step 1: NO2 (g) + NO2 (g) → NO3 (g) + NO (g)

Step 2: NO3 (g) + CO (g) → NO2 (g) + CO2 (g)

Which of the following species is an intermediate?

A. NO3 B. NO C. CO2 D. CO E. NO2


31. Given the following data for the reaction A → B, determine the activation energy, Ea, of the

reaction.k(M/s) T(K)4.05 x 10-3 3506.78 x 10-3 400

A. 0.699 J/mol B. 11.9 kJ/molC. 172 J/mol D. 1.43 kJ/molE. 5.81 J/mol

32. Which point on the energy profile below is the transition state?

A. III B. II C. V D. IV E. I

33. A proposed mechanism for the reaction H2 + 2ICl ---> I2 + 2HCl is

H2 + ICl ---> HI + HCl slow HI + ICl ---> I2 + HCl fast.

What is the molecularity of the rate determining step?

A. zero-molecularB. bimolecularC. termolecularD. unimolecularE. need more information.


34. The mechanism for the first-order reaction

Step 1: H2O2(aq) + I− (aq )→ H2O(l ) + OI− (aq) (slow)

Step 2: H2O2(aq) + OI− (aq) → H2O(l ) + O2(g) + I− (aq) (fast)

Identify the catalyst in the reaction.

A. H2O2 B. O2 C. H2O D. OI- E. I-

35. A proposed mechanism for the reaction H2 + 2ICl ---> I2 + 2HCl is

H2 + ICl ---> HI + HCl slow HI + ICl ---> I2 + HCl fast.

What is the rate law for the second fast step?

A. R = k[I2][HCl]B. R = k([HI][ICl]-[I2][HCl])C. R = k[HI][ICl]2D. R = k[HI][ICl]E. R = k[HI]2[ICl]

36. Which of the following reaction pathways shows the effect of a catalyst (black) on anuncatalyzed reaction (gray)?

A. B.

C. D.

Answer Key for Test “Exam 2 F06 Form A”, 10/17/07No. in

Q-BankNo. onTest Correct Answer

13 10 1 E13 7 2 B13 5 3 D13 16 4 E13 35 5 C13 46 6 D13 49 7 E13 22 8 C13 20 9 C13 55 10 E13 85 11 B13 64 12 D13 84 13 A13 75 14 C13 87 15 C13 91 16 C14 18 17 D14 3 18 C14 98 19 A14 14 20 C14 11 21 A14 26 22 A14 21 23 B14 43 24 D14 25 25 E14 47 26 B14 30 27 D14 40 28 B14 65 29 A14 55 30 A14 84 31 B14 64 32 A14 99 33 B14 94 34 E14 100 35 D14 96 36 B

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