Download 24. The following reaction is at equilibrium

1. The rate law for a reaction with the equation
A + 2B → C + D
is r = k [A]2 [B]. Which of the following statements is NOT CORRECT.
(A) If the initial rate of disappearance of B at a particular time is 0.1 M/s, the initial rate of
disappearance of A is 0.05 M/s?
(B) The overall order of the reaction is 3.
(C) When the concentration of B is left unchanged and that of A is halved, the initial rate will
drop by a factor of two.
(D) If the concentration of B is halved and that of A is doubled at the same time, the initial rate
will double.
(E) If the initial rate of appearance of A at a particular time is 0.1 M/s, the initial rate of
disappearance of B is 0.2 M/s.
2. The diagrams below represent the changes in the make-up of a flask as green molecules react
in a 1st-order process to make red molecules.
Time = 0
What is the rate constant for this reaction?
(A) 10.0 s-1
(B) 0.0693 s-1
(C) 1.73 s-1
(D) 4.80×10-4 s-1
(E) 0.0250 s-1
Time = 10 seconds
3. A student would like to determine the rate constant, k, of a 1st order reaction involving a
single reactant by measuring the change in concentration of the reactant over time.
Which of the following set of X and Y axis choices would allow the student to fit a linear
equation and determine k from the slope?
(A) X axis - [A]t
Y-axis - time
(B) X axis - time
Y-axis - 1/[A]t
(C) X axis - time
Y-axis - [A]t
(D) X axis - time
Y-axis - ln[A]
(E) X axis - 1/[A]t
Y-axis - time
4. A reaction and its rate law are given below. When [C4H6] = 2.0 M, the rate is 0.106 M/s.
What is the rate when [C4H6] = 4.0 M?
2 C4H6  C8H12 Rate = k[C4H6]2
(A)
0.053 M/s
(B)
0.424 M/s
(C)
0.212 M/s
(D)
0.022 M/s
(E)
0.106 M/s
5. Which graph could correctly depict the changes in concentrations for the reaction
2 N2 (g) + 5 O2 (g) + 2 H2O (l) → 4 HNO3 (aq)?
(B)
6. For a 2nd order reaction, with only 1 reactant, what is the concentration after 42.0 seconds, if
the initial concentration of reactant is 5.00 M and the half-life is 27.0 seconds?
(A) 1.36 M
(B) 1.56 M
(C) 1.76 M
(D) 1.96 M
(E) 2.16 M
7. Consider a zero order reaction. How long will it take for only 37% of the reactant to remain
if the starting concentration is 2.00 M and the half life is 7.00 minutes?
(A) 9.02 min.
(B) 8.82 min.
(C) 8.62 min.
(D) 8.42 min.
(E) 8.22 min.
8. Consider the 1st order reaction.
A  2B + C
If you start with 3 M of reactant A, then how long will it take to generate 1 M of product B?
k = 0.0134 /min
(A) 15.3 min.
(B) 20.3 min.
(C) 25.3 min.
(D) 30.3 min.
(E) 35.3 min.
9. Which of the following statements is TRUE?
(A) The half life for zero order reactions do not depend on the initial amount, [A]0.
(B) The half life for first order reactions depend on the initial amount, [A]0.
(C) The half life for second order reactions do not depend on the initial amount, [A]0.
(D) The half life for any order reaction, zero, 1st, or 2nd, does not depend on temperature via the
rate constant.
(E) The half life for any order reaction, zero, 1st, or 2nd, depends on temperature since the rate
constant is only constant for a given temperature.
10.
What distance corresponds to the activation energy for the reaction of X to Y?
(A)
(B)
(C)
(D)
(E)
11.
a
b
c
d
e
Which of the following statements is false?
(A)
Increasing the temperature of a reaction will increase the rate.
(B)
Increasing the number of collisions will increase the rate of reaction.
(C)
Lowering the activation energy will increase the rate of reaction.
(D)
The addition of a catalyst will decrease the rate of a process.
(E)
The addition of a catalyst will lower the activation energy of a process.
12. An Arrhenius plot allows one to determine:
(A) The rate constant, k, of a reaction.
(B) The temperature, T, of a reaction.
(C) The activation energy, Ea, of a reaction.
(D) The frequency factor, A, of a reaction.
(E) The activation energy, Ea, as well as the frequency factor, A.
13. The activation energy of a reaction is 75kJ/mol and the frequency factor is 1 x 1010 s-1.
H2O2  O2 + H2O
Given that this is a 1st order reaction with respect to H2O2 and that it occurs at 298 K
What is the instantaneous rate of H2O2 decomposition at the moment when [H2O2] = 1 M
(A) 0.007 M/s
(B) 0.015 M/S
(C) 9.5 x 109 M/s
(D) 5.0 x 105 M/s
(E) 0.5 M/s
14. Which of the following statements is TRUE.
(A) Lowering the temperature will speed up most reactions.
(B) A catalyst has to be continuously supplied as it is consumed during a reaction.
(C) The activation energy of a reaction measures the frequency with which reactants collide.
(D) A catalyst lowers the activation energy of a reaction.
(E) Increasing the surface area of a reaction involving a solid will slow down the reaction.
15. The equilibrium law expression for the reaction 2 NO2 (g)  O2 (g) + 2 NO (g) is:
(A)
Kc =
[O2 ][ NO]
[ NO2 ]2
(B)
Kc =
[O2 ] 2 [ NO]
[ NO2 ] 2
(C)
Kc =
[O2 ][ NO]2
[ NO2 ]2
(D)
Kc =
[O2 ][ NO]
[ NO2 ]
(E)
[ NO 2 ]2
Kc =
[ NO]2 [O 2 ]
16. Which of the following statements is NOT CORRECT?
(A) If Keq = 1 for the reaction A  B, the equilibrium mixture will contain 50% products and
50% reactants.
(B) If Keq >> 1 you will have very little reactant left at equilibrium.
(C) If K is the equilibrium constant for the reaction A2B, the equilibrium constant for the
reverse reaction is equal to ½ K.
(D) If Keq << 1 you will have lots of reactant left at equilibrium.
(E) If Keq for a particular reaction is 10, the equilibrium constant for the reverse reaction is -10.
17. An undergraduate researcher has been studying chlorination reactions and measuring the
pressure of Cl2 gas present once equilibrium has been established at 300 K.
Which of the 5 studied reactions favors the formation of product the most?
(A) P (s) + 2.5Cl2 (g)  PCl5 (s)
PCl2 gas = 1 atm.
(B) Zr (s) + 2 Cl2 (g)  ZrCl4 (s)
PCl2 gas = 0.5 atm.
(C) Al (s) + 1.5 Cl2 (g)  AlCl3 (s)
PCl2 gas = 0.1 atm.
(D) Ca (s) + Cl2 (g)  CaCl2 (s)
PCl2 gas = 0.01 atm.
(E) We cannot answer; we need more information about the concentrations of the solids.
18. A 1000 liter reaction vessel at 500 K is filled with Cl2 and H2. At equilibrium it contains
70.9 grams of Cl2 and 2 grams of H2. We can assume ideal gas behavior for H2 and Cl2.
H2 (g) + Cl2 (g)  2HCl (g)
Kp = 1 x 105
What is the partial pressure of HCl in the vessel at equilibrium?
(A) 57.5 atm.
(B) 165 atm.
(C) 12.9 atm.
(D) 34.8 atm.
(E) 17.0 atm
19. What is the relationship between Kp and Kc for the reaction, 2ICl(g)
(A)
(B)
(C)
(D)
(E)
I2(g) + Cl2(g)?
Kp = Kc(RT)-1
Kp = Kc
Kp = Kc(RT)
Kp = Kc(2RT)
Kp = Kc(RT)2
20. NO is placed in a one liter flask at 2273 K. After equilibrium is attained, 0.200 mol NO,
0.0863 mol N2 and 0.0863 mol O2 are present. What is Kc for this reaction?
2NO(g)
(A)
(B)
(C)
(D)
(E)
N2(g) + O2(g)
9.92
39.7
3.15
0.576
0.0372
21. Sulfur hexafluoride is an industrially important “inert gas” used inside insulated windows
panes. A student is studying the equilibrium levels of S2F10, a highly toxic gas, which may form
inside windows from SF6 decomposition.
2 SF6 (g)  S2F10 (g) + F2 (g)
Kp ≈ 1.5 x 10-15
at 298 K
After equilibrium is established the student measures the partial pressure to be 700 torr for SF6
and 5 x 10-6 torr for F2.
What is the partial pressure of S2F10 (g) inside the insulated window?
(A)
2.1 x 10-9 torr
(B)
2.1 x 10-7 torr
(C)
2.1 x 10 -5 torr
(D)
2.1 x 10 -3 torr
(E)
2.1 x 10 -1 torr
22. The following statements refer to a mixture (reaction quotient Q) that is prepared and then
allowed to come to equilibrium. Which statement is NOT CORRECT?
(A) A reaction will proceed to make the value of Q approach that of K.
(B) If Q = K there is no change.
(C) If Q > K, the reaction goes to the left.
(D) The system will never come to equilibrium.
(E) If Q < K for a particular reaction, the final equilibrium mixture will have more reactants
than the original mixture.
23. Syngas, a mixture of CO and H2 gases, is very industrially important.
C(s) + H2O(g) → CO(g) + H2(g)
∆H= 323.1 kJ/mol (endothermic) at 298 °C
If a chemical engineer needed to maximize the amount of CO and H2 produced so they could
keep their job, which of the following might they try once the reaction vessel has reached
equilibrium?
(A) Lower the reaction vessel temperature.
(B) Add more C to the reaction vessel.
(C) Remove steam, H2O (g), from the reaction vessel.
(D) Increase the volume of the reaction vessel.
(E) Decrease the volume of the reaction vessel.
24. The following reaction is at equilibrium:
2 SO3 (g)
(A)
(B)
(C)
2 SO2 (g) + O2 (g)
The concentration of O2 (g) increases when the system pressure is increased
The concentration of O2 (g) decreases when the system pressure is increased
The concentration of O2 (g) stays the same the system pressure is increased
25.
The following reaction is at equilibrium:
2HBr (g)  H2 (g) + Br2 (g)
(A)
(B)
(C)
26.
ΔHo = +72 kJ (endothermic)
The concentration of Br2 (g) increases when the system is heated
The concentration of Br2 (g) decreases when the system is heated
The concentration of Br2 (g) stays the same when the system is heated
The following reaction is at equilibrium:
2HBr (g)  H2 (g) + Br2 (g)
(A)
(B)
(C)
ΔHo = +72 kJ (endothermic)
The concentration of H2 (g) increases when Br2 (g) is added
The concentration of H2 (g) decreases when Br2 (g) is added
The concentration of H2 (g) stays the same when Br2r (g) is added
ANSWER KEY FOLLOWS BELOW
1. The rate law for a reaction with the equation
A + 2B → C + D
is r = k [A]2 [B]. Which of the following statements is NOT CORRECT.
(A) If the initial rate of disappearance of B at a particular time is 0.1 M/s, the initial rate of
disappearance of A is 0.05 M/s?
(B) The overall order of the reaction is 3.
(C) When the concentration of B is left unchanged and that of A is halved, the initial rate
will drop by a factor of two.
(D) If the concentration of B is halved and that of A is doubled at the same time, the initial rate
will double.
(E) If the initial rate of appearance of A at a particular time is 0.1 M/s, the initial rate of
disappearance of B is 0.2 M/s.
2. The diagrams below represent the changes in the make-up of a flask as green molecules react
in a 1st-order process to make red molecules.
Time = 0
What is the rate constant for this reaction?
(A) 10.0 s-1
(B) 0.0693 s-1
(C) 1.73 s-1
(D) 4.80×10-4 s-1
(E) 0.0250 s-1
Time = 10 seconds
3. A student would like to determine the rate constant, k, of a 1st order reaction involving a
single reactant by measuring the change in concentration of the reactant over time.
Which of the following set of X and Y axis choices would allow the student to fit a linear
equation and determine k from the slope?
(A) X axis - [A]t
Y-axis - time
(B) X axis - time
Y-axis - 1/[A]t
(C) X axis - time
Y-axis - [A]t
(D) X axis - time
Y-axis - ln[A]
(E) X axis - 1/[A]t
Y-axis - time
4. A reaction and its rate law are given below. When [C4H6] = 2.0 M, the rate is 0.106 M/s.
What is the rate when [C4H6] = 4.0 M?
2 C4H6  C8H12 Rate = k[C4H6]2
(A)
0.053 M/s
(B)
0.424 M/s
(C)
0.212 M/s
(D)
0.022 M/s
(E)
0.106 M/s
5. Which graph could correctly depict the changes in concentrations for the reaction
2 N2 (g) + 5 O2 (g) + 2 H2O (l) → 4 HNO3 (aq)?
(B)
6. For a 2nd order reaction, with only 1 reactant, what is the concentration after 42.0 seconds, if
the initial concentration of reactant is 5.00 M and the half-life is 27.0 seconds?
(A) 1.36 M
(B) 1.56 M
(C) 1.76 M
(D) 1.96 M
(E) 2.16 M
7. Consider a zero order reaction. How long will it take for only 37% of the reactant to remain
if the starting concentration is 2.00 M and the half life is 7.00 minutes?
(A) 9.02 min.
(B) 8.82 min.
(C) 8.62 min.
(D) 8.42 min.
(E) 8.22 min.
8. Consider the 1st order reaction.
A  2B + C
If you start with 3 M of reactant A, then how long will it take to generate 1 M of product B?
k = 0.0134 /min
(A) 15.3 min.
(B) 20.3 min.
(C) 25.3 min.
(D) 30.3 min.
(E) 35.3 min.
9. Which of the following statements is TRUE?
(A) The half life for zero order reactions do not depend on the initial amount, [A]0.
(B) The half life for first order reactions depend on the initial amount, [A]0.
(C) The half life for second order reactions do not depend on the initial amount, [A]0.
(D) The half life for any order reaction, zero, 1st, or 2nd, does not depend on temperature via the
rate constant.
(E) The half life for any order reaction, zero, 1st, or 2nd, depends on temperature since the
rate constant is only constant for a given temperature.
10.
What distance corresponds to the activation energy for the reaction of X to Y?
(A)
(B)
(C)
(D)
(E)
11.
a
b
c
d
e
Which of the following statements is false?
(A)
Increasing the temperature of a reaction will increase the rate.
(B)
Increasing the number of collisions will increase the rate of reaction.
(C)
Lowering the activation energy will increase the rate of reaction.
(D)
The addition of a catalyst will decrease the rate of a process.
(E)
The addition of a catalyst will lower the activation energy of a process.
12. An Arrhenius plot allows one to determine:
(A) The rate constant, k, of a reaction.
(B) The temperature, T, of a reaction.
(C) The activation energy, Ea, of a reaction.
(D) The frequency factor, A, of a reaction.
(E) The activation energy, Ea, as well as the frequency factor, A.
13. The activation energy of a reaction is 75kJ/mol and the frequency factor is 1 x 1010 s-1.
H2O2  O2 + H2O
Given that this is a 1st order reaction with respect to H2O2 and that it occurs at 298 K
What is the instantaneous rate of H2O2 decomposition at the moment when [H2O2] = 1 M
(A) 0.007 M/s
(B) 0.015 M/S
(C) 9.5 x 109 M/s
(D) 5.0 x 105 M/s
(E) 0.5 M/s
14. Which of the following statements is TRUE.
(A) Lowering the temperature will speed up most reactions.
(B) A catalyst has to be continuously supplied as it is consumed during a reaction.
(C) The activation energy of a reaction measures the frequency with which reactants collide.
(D) A catalyst lowers the activation energy of a reaction.
(E) Increasing the surface area of a reaction involving a solid will slow down the reaction.
15. The equilibrium law expression for the reaction 2 NO2 (g)  O2 (g) + 2 NO (g) is:
(A)
Kc =
[O2 ][ NO]
[ NO2 ]2
(B)
Kc =
[O2 ] 2 [ NO]
[ NO2 ] 2
(C)
Kc =
[O2 ][ NO]2
[ NO2 ]2
(D)
Kc =
[O2 ][ NO]
[ NO2 ]
(E)
[ NO 2 ]2
Kc =
[ NO]2 [O 2 ]
16. Which of the following statements is NOT CORRECT?
(A) If Keq = 1 for the reaction A  B, the equilibrium mixture will contain 50% products and
50% reactants.
(B) If Keq >> 1 you will have very little reactant left at equilibrium.
(C) If K is the equilibrium constant for the reaction A2B, the equilibrium constant for
the reverse reaction is equal to ½ K.
(D) If Keq << 1 you will have lots of reactant left at equilibrium.
(E) If Keq for a particular reaction is 10, the equilibrium constant for the reverse reaction is -10.
17. An undergraduate researcher has been studying chlorination reactions and measuring the
pressure of Cl2 gas present once equilibrium has been established at 300 K.
Which of the 5 studied reactions favors the formation of product the most?
(A) P (s) + 2.5Cl2 (g)  PCl5 (s)
PCl2 gas = 1 atm.
(B) Zr (s) + 2 Cl2 (g)  ZrCl4 (s)
PCl2 gas = 0.5 atm.
(C) Al (s) + 1.5 Cl2 (g)  AlCl3 (s)
PCl2 gas = 0.1 atm.
(D) Ca (s) + Cl2 (g)  CaCl2 (s)
PCl2 gas = 0.01 atm.
(E) We cannot answer; we need more information about the concentrations of the solids.
18. A 1000 liter reaction vessel at 500 K is filled with Cl2 and H2. At equilibrium it contains
70.9 grams of Cl2 and 2 grams of H2. We can assume ideal gas behavior for H2 and Cl2.
H2 (g) + Cl2 (g)  2HCl (g)
Kp = 1 x 105
What is the partial pressure of HCl in the vessel at equilibrium?
(A) 57.5 atm.
(B) 165 atm.
(C) 12.9 atm.
(D) 34.8 atm.
(E) 17.0 atm
19. What is the relationship between Kp and Kc for the reaction, 2ICl(g)
(A)
(B)
(C)
(D)
(E)
I2(g) + Cl2(g)?
Kp = Kc(RT)-1
Kp = Kc
Kp = Kc(RT)
Kp = Kc(2RT)
Kp = Kc(RT)2
20. NO is placed in a one liter flask at 2273 K. After equilibrium is attained, 0.200 mol NO,
0.0863 mol N2 and 0.0863 mol O2 are present. What is Kc for this reaction?
2NO(g)
(A)
(B)
(C)
(D)
(E)
N2(g) + O2(g)
9.92
39.7
3.15
0.576
0.0372
21. Sulfur hexafluoride is an industrially important “inert gas” used inside insulated windows
panes. A student is studying the equilibrium levels of S2F10, a highly toxic gas, which may form
inside windows from SF6 decomposition.
2 SF6 (g)  S2F10 (g) + F2 (g)
Kp ≈ 1.5 x 10-15
at 298 K
After equilibrium is established the student measures the partial pressure to be 700 torr for SF6
and 5 x 10-6 torr for F2.
What is the partial pressure of S2F10 (g) inside the insulated window?
(A)
2.1 x 10-9 torr
(B)
2.1 x 10-7 torr
(C)
2.1 x 10 -5 torr
(D)
2.1 x 10 -3 torr
(E)
2.1 x 10 -1 torr
22. The following statements refer to a mixture (reaction quotient Q) that is prepared and then
allowed to come to equilibrium. Which statement is NOT CORRECT?
(A) A reaction will proceed to make the value of Q approach that of K.
(B) If Q = K there is no change.
(C) If Q > K, the reaction goes to the left.
(D) The system will never come to equilibrium.
(E) If Q < K for a particular reaction, the final equilibrium mixture will have more
reactants than the original mixture.
23. Syngas, a mixture of CO and H2 gases, is very industrially important.
C(s) + H2O(g) → CO(g) + H2(g)
∆H= 323.1 kJ/mol (endothermic) at 298 °C
If a chemical engineer needed to maximize the amount of CO and H2 produced so they could
keep their job, which of the following might they try once the reaction vessel has reached
equilibrium?
(A) Lower the reaction vessel temperature.
(B) Add more C to the reaction vessel.
(C) Remove steam, H2O (g), from the reaction vessel.
(D) Increase the volume of the reaction vessel.
(E) Decrease the volume of the reaction vessel.
24. The following reaction is at equilibrium:
2 SO3 (g)
(A)
(B)
(C)
2 SO2 (g) + O2 (g)
The concentration of O2 (g) increases when the system pressure is increased
The concentration of O2 (g) decreases when the system pressure is increased
The concentration of O2 (g) stays the same the system pressure is increased
25.
The following reaction is at equilibrium:
2HBr (g)  H2 (g) + Br2 (g)
(A)
(B)
(C)
26.
ΔHo = +72 kJ (endothermic)
The concentration of Br2 (g) increases when the system is heated
The concentration of Br2 (g) decreases when the system is heated
The concentration of Br2 (g) stays the same when the system is heated
The following reaction is at equilibrium:
2HBr (g)  H2 (g) + Br2 (g)
(A)
(B)
(C)
ΔHo = +72 kJ (endothermic)
The concentration of H2 (g) increases when Br2 (g) is added
The concentration of H2 (g) decreases when Br2 (g) is added
The concentration of H2 (g) stays the same when Br2r (g) is added