Differentiated Chemistry: Ch

Differentiated Chemistry: Ch. 14 & 15 Take Home TestName:

Multiple Choice. Select the best answer for the following. YOU ABSOLUTELY MUST SHOW YOUR WORK OR THERE IS NO CREDIT!!!!!!

1. ____In the reaction, 2NO2  2NO + O2 at 300oC, [NO2] drops from 0.0100 to 0.00650 M in 1.0 x 102s. What is the average rate of appearance of O2 for this period in M/s?

a. 0.000018b. 0.000035c. 0.000070d. 0.0035e. 0.0070

2. ____ Use the table of data shown to calculate the average rate of reaction between 10 s and 30 s for A+BC

Time (s) / 0 / 10 / 20 / 30 / 40
[A] mol/L / 0.124 / 0.110 / 0.088 / 0.073 / 0.054

a. 0.0012M/sb. –0.0019 M/sc. 0.0019M/sd. –0.0012 M/s

3. ____If the reaction 2A + 3D  products is first order in A and second-order in D, then the rate law will

have the form, Rate =

a. k[A][D]b. k[A]2[D]3c. k[A][D]2d. k[A]2[D]e. k[A]2[D]2

4. ____A reaction was found to be zero order in A. What effect will tripling the concentration of A have on the

reaction rate?

a. remains constantb. increases by a factor of 27c. increases by a factor of 9

d. triplese. decreases by the cube root of 3

5. ____Which of the following graphs is linear for aA  products?

a. ln[A] vs. t if 1o in Ab. ln[A] vs. t if 2o in A c. 1/[A] vs. t if 1o in A

d. [A]2 vs. tif 2o in A e. 1/[A]2 vs. t if 2o in A

6. ____The reaction rate constant for a particular second order reaction is 0.47 M-1s-1. If the initial concentration of the reactant is 0.25 mol/L, how many seconds will it take for the concentration to decrease to 0.13 mol/L?

a. 7.9b. 1.4c. 3.7d. 1.7e. none of the above

7. ____The half-life for a certain first order reaction is 13 minutes. If the initial concentration of the reactant is 0.085 M, how many minutes will it take for it to decrease to 0.055M?

a. 8.2b. 11c. 3.6d. 0.048e. 24

8. ____Calculate the rate constant of a first order process that has a half-life of 225 s.

a. 0.693 s-1b. 3.08 x 10-3 s-1c. 1.25 s-1d. 5.89 x 104 s-1

9. ____The reaction rate depends upon

a. collision frequencyb. collision energyc. collision orientationd. all the above

10. ___In the potential energy profile (energy diagram) of a reaction, the species that exists at the maximum on

the curve is called the

a. productb. transition statec. activation energyd.reactant

11. ___ In the Arrhenius equation, _____ is the frequency factor

a. kb. Ac. ed. Eae. Rf. T

12. ___What is the intermediate in the following mechanism?

A + B  C + D

B + D  X

a. Ab. Bc. Cd. De. X

13. ___The first step of a mechanism involving the reactant I2 is shown. The expression relating [I] to [I2] is

k 1

I2 2I fast, equilibrium

k -1

a. [I] = k 1 [I2]b. [I] = k 1 [I2]1/2 c. [I] = (k 1/ k –1)1/2[I2]1/2

d. [I] = (k 1/ k –1)2[I2]2e. [I] = (k 1/ k –1)2[I2]1/2

14. ___Consider the following hypothetical chemical reaction: 2A + 2B  C. The mechanism for this reaction

is:1)A + B  D (slow)

2)D + B  E (fast)

3) A + E  C (fast)

Which of the following is the correct rate law for this reation?

a. Rate = k [A][B]b. Rate = k[A][E]c. Rate = k[A]2[B]2d. Rate = k [D][B]

15. ___ Which of the following will change the value of an equilibrium constant?

a. changing temperature b. adding other substances that are not reactants

c. varying initial concentrations of reactantsd. varying initial concentrations of products

16. ___For the gas-phase reaction, CO(g) + 3H2(g) CH4(g) + H2O(g), which expression represents Keq

correctly?

a. [CO]3 [H2] / [CH4][H2O]b. [CO] [H2] 3 / [CH4][H2O]c. [CH4][H2O] / [CO] [H2]3

d. [CH4][H2O] / [CO]3 [H2]e. [CH4][H2O] / [CO] ( 3[H2])3

17. ___The balanced homogeneous vapor-phase reaction A + B  X + Y has a Keq = 997 at 472 K. At

equilibrium:

a. products predominateb. reactants dominatec. reactants are equal to products

d. only products existe. only reactants exist

18. ___Calculate Keq for the following reaction if the equilibrium concentrations of H2, CO, and H2O are

2.0 x 10-2 M, 2.0 x 10-2 M and 5.0 x 10-2 M respectively:

C(s) + H2O(g) CO(g) + H2(g)

a. 0.0080b. 5.0 x 10-3c. 12.5d. 200

19. ___Assume that Keq = 3.0 x 105 for the following reaction at 25 oC. What is Kp for

2H2S(g) + 3O2(g)  2H2O(g) + 2SO2(g)

a. 1.2 x 104b. 8.2 x 10-5c. 3.3 x 10-6d. 3.0 x 105

20. ___A 2.21 L vessel was found to contain 4.18 x 10-2 mol of CO2, 2.81 x 10-2 mol of CO, and 8.89 x 10-3

mol of O2. Is the system at equilibrium for the following reaction? If not, which direction must the reaction proceed? 2CO2(g)  2CO(g) + O2(g) Keq = 1.2 x 10-13

a. yesb. no, to the rightc. no, to the left

21. ___Which of the following processes would have a positive S value?

Ca(OH)2(s) + 2HCl(g) CaCl2(s) + 2H2O(g)
CO2(s) CO2(g)
H2(g) + Cl2(g)  2HCl(g)
N2(g) + 3H2(g)  2NH3(g)

22. ___Consider the following table of thermodynamic data. All values are tabulated for 25oC.

Substance / Gof (kJ/mol) / Sof(J/mol K) / Substance / Gof (kJ/mol) / Sof(J/mol K)
C2H2(g) / 209 / 201 / H2(g) / 0 / 131
C2H4(g) / 68 / 219 / H20(g) / -229 / 189
C2H6(g) / -33 / 230 / C2H5OH(l) / -175 / 161

Determine the value of Ho for the following reaction at 25oC. C2H4(g) + H20(g)  C2H5OH(l)

a. –88 kJ/molb. –175 kJ/molc. –14 kJ/mold. –0.247 kJ/mol

23. ___A reaction has Ho and So of 137 kJ and 120 J/K, respectively. The reaction will be:

spontaneous at all temperaturesc. spontaneous at low temperatures

b. spontaneous at high temperaturesd. nonspontaneous at all temperatures.

24. ___Under certain conditions, the equilibrium constant for the decomposition of PCl5(g) into PCl3(g) and Cl2(g) is

0.0211 mol/L. What is the equilibrium concentration of PCl3(g) when the initial concentration of PCl5 was 1.00M?

a. 0.86 Mb. 1.00 Mc. 0.135 Md. 0.021 Me. none of the above

25. For the combustion of methane (CH4), find Hfo, Sfo, and Gfo at 25oC. (Use the table below

BONUS: A scientific journal reports on a platinum-containing catalyst that is proposed to increase ammonia production from hydrogen and nitrogen by 100 times than that reported by Born & Haber. What do you think about the report? Be sure to be state a position and explain why.

Compound / Hfo (kJ/mol) / Sfo (J/mol K) / Compound / Hfo (kJ/mol) / Sfo (J/mol K)
CH4(g) / -74.8 / 186.3 / H2(g) / 0 / 130.58
CO2(g) / -393.5 / 213.6 / O(g) / 247.5 / 161.0
C2H4(g) / 52.30 / 219.4 / C(g) / 718.4 / 158.0
O2(g) / 0 / 205.0 / CO(g) / -110.5 / 197.9
H2O(g) / -241.82 / 188.83

ln[A]t = -kt + ln[A]01/[A]t = kt + 1/[A]0t1/2 = 1/ k[A]0PV = nRT

t1/2 = - ln(1/2) / kD = m/ Vk = A e –Ea/RTln(k1/k2) = Ea/R (1/T2 – 1/T1)

K9p= yucKKp = Keq(RT)n-b + (b2-4ac)^½