Chemistry Exam Green

Topics: Chemical kinetics, Rate equation, Chemical reaction Pages: 8 (1780 words) Published: February 22, 2013
CHEM 188 – Spring, 2013
Hour Exam 1 (Red)

February 14, 2011


Your scantron answer sheet must show your NAME, 7-DIGIT KU ID NUMBER, and LAB SECTION. (Begin these entries at the LEFT end of the space provided.)

In answering the questions, be careful to fill in the corresponding circles on the answer sheet according to the number of the question on the exam. USE A SOFT (No. 2) PENCIL. ((((((((((((((((((((((((((((((((((((((

Useful information:

Gas constant, R = 8.314 J/K ( mol

= 0.08206 L ( atm/K ( mol

Integrated Rate Laws:

Arrhenius equation: [pic]


Relation of KP to KC: KP = KC(RT)(n

Quadratic formula: [pic]

1.Consider the reaction

4PH3(g) ( P4(g) + 6H2(g).

Suppose that, at a particular moment during the reaction, H2(g) is being formed at the rate of 0.624M/s. At what rate is P4(g) being formed?

A. 0.013 M/sB. 0.026 M/sC. 0.052 M/sD. 0.104 M/sE. 0.624 M/s

2.Consider the hypothetical reaction A + 2B ( products. Use the following data to determine the rate constant, k, for the reaction.

Expt. # [A]0 [B]0 Initial rate
1 0.20 0.20 2.19 M/min
2 0.20 0.40 2.19 M/min
3 0.40 0.20 4.38 M/min

A. 3.8 min-1 B. 7.3 min-1C. 11 min-1 D. 22 min-1 E. 26 min-1

3.If concentration is expressed in units of molecules per cubic centimeter (molec/cm3) and time in units of seconds (s), the units of a zero-order rate constant are

A. molec cm( 3 s( 1B. cm6 molec( 2 s( 1 C. s ( 1

D. s ( 2 E. cm3 molec( 1 s( 1

4.The chemical reaction A ( products is known to have a rate law of the general type

rate = k[A]n.

A plot of [A] versus time was found to give a straight line with a negative slope. What is n, the order of reaction?

A. zeroB. firstC. secondD. thirdE. none of these

5.At 25oC, the second-order reaction

NOCl(g) ( NO(g) + ½ Cl2(g)

is 50% complete after 26 hours when the initial concentration of NOCl is 1.00 mol/L. How long will it take for the reaction to be 75% complete?

A. 26 hrB. 39 hrC. 52 hrD. 78 hrE. 156 hr

6.What is the half-life of a compound if 34 percent of a given sample of the compound decomposes in 10 min? Assume first-order kinetics.

A. 13 minB. 17 min C. 23 minD. 35 minE. 66 min
7.The reaction

NOCl(g) ( NO(g) + ½ Cl2(g)

is second-order in [NOCl] with a rate constant, k, of 0.040 M(1hr(1at 25oC. If the initial concentration of NOCl were 4.00 M, what would be the concentration of NOCl after 25 hrs?

A. 3.0 MB. 2.4 MC. 1.8 MD. 1.2 ME. 0.80 M

8.Given that Ea for a certain biological reaction is 52 kJ/mol, and that the rate constant, k, is 3.7 x 10(2 s (1 at 15oC, what is the rate constant at 37oC?

A. 0.087 s (1B. 0.12 s (1 C. 0.17 s (1

D. 0.24 s (1E. 0.36 s (1

9.For a certain reaction, raising the temperature from 25oC to 45oC increases the value of the rate constant, k, by a factor of 1.25. What is the activation energy, Ea, for this reaction in units of kJ/mol?

A. 8.8B. 24.2C. 33.7D. 44.9E. 55.6

10.A particular catalyst increases the rate of a certain reaction by a factor 5.00 x 103 at 25oC. By how much (kJ/mol) must this catalyst have lowered the activation energy for this reaction? (Assume the frequency factor remains the same.)

A. 17.1 kJ/molB. 21.1 kJ/molC. 25.1 kJ/molD. 29.1 kJ/molE. 33.1 kJ/mol

11.The overall reaction

A + B ( C + D

is thought to occur by the following three-step mechanism:

(1) A + E ( F + G
(2) B + F ( H + C
(3) G + H ( E + D

Identify the intermediate(s) in the proposed mechanism.

A. EB. E & GC. E, G & FD. F, G & HE. E, G & H

12.Which statement correctly describes the effect of...
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