Name______Solutions, kinetics, and non-aqueous equilibrium
1. Cyclobutane decomposes in a first order reaction to form butadiene. At a particular temperature the pressure of the cyclobutane in a vessel drops to 1/8 its original value in 46.0 seconds. What is the half life for this reaction at this temperature?
A) 5.75 s B) 11.5 s C) 15.3 s D) 23 s E) 46 s
2. The reaction A + B ➞C is found to be first order for A, and second order for B.
The instantaneous rate of formation of C in a certain experiment is 0.400 M/s. The experiment is repeated, with twice the concentration of A, but one half the concentration of B in the first experiment. The new rate of formation of C would be
A) 0.100 M/s B) 0.200 M/a C) 0.400 M/s D) 0.800 M/s E) 1.60 M/s
3. H2(g) + F2(g) ⇄ 2 HF (g) ΔH > 0
Which of the following changes to the system will decrease the quantity of HF in the equilibrium mixture?
I. Adding H2 (g)
II. Decreasing the temperature
III. Decreasing the pressure
A) I onlyB) I and II onlyC) II only D) II and III only E) I, II, and III
4. Which of the following methods of expressing concentration changes with temperature?
A) mass % B) mole fraction C) molarity D) molality E) mass parts per million
5. 684 mg of sucrose, (molar mass 342 g) is dissolved to prepare 400. mL of an aqueous solution. What is the molarity of 200. mL of this solution?
A) 0.00500 M B) 0.00250 M C) 0.00750 M D) 0.0100 M E) 0.25 M
6. Factors that affect the rate of a chemical reaction include which of the following?
I. Frequency of molecular collisions
II. Kinetic energy of molecular collisions
III. Orientation of reactant particles during collisions.
A) II only B) I and II only C) I and III only D) II and III only E) I,II, and III
7. If the unit for the rate constant for a reaction is atm2 sec1 the overall rate order for that reaction is A) zero B) first C) second D) third E) fourth
8. If a first order reaction has a half life of 693 seconds, what is the numerical value of the rate constant for that reaction? A) 0.00100 B) 1000. C) 693 D) 0.693 E) 1.000
Choices for questions 9 -13.
A. Zero order only
B. First order only
C. Second order only
D. First and second order, but not zero order
E. Zero, first, and second order
9. Has a constant half life at constant temperature
10. The rate law produced by a single, bimolecular step
11. The time needed to use up half of an original sample decreases with increasing temperature.
12. A graph of concentration vs. time produces a straight line.
13. The initial rate is faster than all subsequent rates
14. The reaction 2 H2 + 2 NO 2 H2O + N2 (all gases) is found, at a certain temperature to obey the rate law Rate = k[H2][NO]2, where k= 3.00 x 10-2 M2/s for the production of N2 . What is the rate of production of N2 when both the hydrogen and the NO are 0.200 molar? ( in M/s)
A) 0.00120 B) 2.40 x 104 C) 4.80 x104 D) 4.80 x 105 E) 18.75
15. At 1000 K the Kc for a reaction represented by the equation
2 A(g) + 2 B(g) ⇄ 2 C(g) + D(g) is 0.821 . What is the Kp for the reaction at that same temperature?
A) 0.0100 B) 67.4 C) 0.100 D) 821 E) 0.821
16. What is the molality of a solution that contains 20.0 grams of NaOH dissolved in 200. grams of water? A) 10.0 m B) 2.50 m C) 0.100 m D) 1.00 m
E) 0.00250 m
17. What is the mole fraction of ethanol in an aqueous solution that is
8.00 molal in ethanol? A) 0.800 B) 0.144 C) 0.126 D) 0.250
E) 0. 874
18. What is the molality of HCl in an aqueous solution that is 30.0 % HCl by mass?
A) 11.7 m B) 1.17 m C) 0.822 m D) 0.0822 m E) cannot be calculated unless the density of the solution is given
Questions 19 to 24 are based on the reaction N2(g) + 3 H2(g) 2 NH3(g).
At 298 K, the Kp for this reaction is 6.7 x 105 . ΔH° for the reaction as written is 92 kJ.
Choices: ( for questions 19 to 22)
A. increase the temperature
B. decrease the temperature
C.decrease the volume of the container in which the reaction is
occurring.
D. Increase the container volume
E. Add a catalyst.
19. Which method would increase the rate constant of the reaction?
20. Which method would increase the equilibrium constant of the reaction?
21. Which method would increase the reaction rate without affecting the equilibrium concentrations?
22. Which method would produce a larger yield of ammonia at equilibrium, but would NOT change the equilibrium constant?
23. If at equilibrium at 298 K the pressure of nitrogen is .0200 atm, and the pressure of hydrogen is 0.0300 atm, what pressure of ammonia gas is needed to maintain equilibrium? A) 0.601 B) 0.362 C) 20.04 D) 4.48 E) 0.300
24. If at a certain temperature, the instantaneous rate of formation of ammonia
is 0.0200 atm/minute, what is the instantaneous rate of disappearance of hydrogen under the same conditions?
A) 0.0200 atm/minB) 0.015 atm/minC) 0.0300 atm/min
D) 0.013 atm/min E) 0.0600 atm/min
25. Given that the freezing pt. depression constant for water is 1.86°/m, what is the freezing point of a 0.200 molal aqueous solution of KCl ?
A) 0.372° B) 0.372° C) 0.744° D) 0.744° E) 0.186°
26. Solid ammonium carbonate decomposes at high temperatures.
(NH4)2CO3(s) ⇄ 2 NH3(g) + CO2(g) + H2O(g)
A sample of the solid is placed in an empty, sealed container. At equilibrium it is found that the concentration of ammonia in the container is 4.00 molar. What is the Kc at that temperature? A) 16 B) 32 C) 64 D) 256 E) 512
27. Assuming that the reaction 2 NO2(g) ➞ N2O4(g) is second order. Which statement about the rate constant, k, is most accurate?
A) a graph of the pressure of NO2 vs. time would produce a straight line, of slope equal to -k
B) A graph of Ln (P NO2) vs. time would produce a straight line, with slope equal to -k
C) A graph of Ln (P NO2) vs. time would produce a straight line, with slope equal to k
D) A graph of 1/PNO2 vs time would produce a straight line, with slope equal to k
E) A graph of 1/PNO2 vs time would produce a straight line, with slope equal to k
28. Which aqueous solution would have the highest normal boiling point?
A) 0.10 m CaCl2 B) 0.20 m C2H5OH C) 0.10 m Fe(NO3)3
D) 0.20 m Na2SO3 E) 0.20 m KClO4
Part II
I. . A(aq) + 2 B(aq) 3 C(aq) + D(aq) (10 points)
For the reaction above, carried out in solution of 30C, the following kinetic data were obtained:
Experiment / Initial Conc. of Reactants(mole.liter-1) / Initial Rate of formation of D
(mole.liter-1.min-1)
Ao / Bo
1 / 0.240 / 0.480 / 4.00
2 / 0.240 / 0.120 / 0.250
3 / 0.360 / 0.240 / 1.50
4 / 0.120 / 0.120 / 0.125
5 / 0.240 / 0.0600 / 0.0625
6 / 0.0140 / 1.35 / ?
7 / 0.480 / ? / 4.00
a) Write the rate law expression for this reaction. (Show how you obtained your rate orders)
b) Calculate the value of the specific rate constant, k, and include correct units.
c) Find the value of the initial rate of this reaction in experiment 6
d) Find the concentration of B in experiment 7.
II.. Consider the reaction C(s) + CO2(g) ⇄ 2 CO(g) + heat.
(ΔH° is < 0 )
A. Predict the effect of each of the following changes on the equilibrium quantity of CO (g). Briefly explain each prediction. (10 points)
1. Decreasing the container volume.
2. Decreasing the temperature
3. Increasing the quantity of carbon in the system
4. Adding a catalyst to the system.
B. The system has reached equilibrium. What would now be the effect on the quantity of carbon of removing some CO2 from the system?
III. At 90.0° the vapor pressure of water is 600. torr. A solution is prepared at 90.0° by dissolving 360 grams of glucose, C6H12O6 in 180. grams of water. The solution has a density of 1.24 g/mL . (12 points)
FindA. The % glucose in the solution by mass
B. The mole fraction of water in the solution
C. The vapor pressure of the solution at 90.0° .
D. The molarity of the glucose solution
E. The molality of the glucose
F. The normal boiling point of the solution, given that the boiling pt. elevation constant in water is 0.52°/m .
IV. 0.200 mol of H2 and 0.200 mol of NO are placed together in a
2.0 liter vessel. The following equilibrium is established:
2 NO(g) + 2 H2(g) ⇌ N2(g) + 2 H2O (g)
At equilibrium, the concentration of NO is 0.062 molar. (8 points)
a) calculate the equilibrium concentrations of H2(g) , N2(g) , and H2O (g)
b) Find the Kc of the reaction.
V A certain reaction occurs through the following two step mechanism.
1. NO(g) + NO(g) ➞ N2O2(g)
2. N2O2(g) + H2(g)➞ N2O(g) + H2O(g)
A. Write the overall balanced equation for the net reaction. (2)
B. Write a rate law for each of the two elementary steps shown above. (4)
C. Identify any intermediate in the mechanism. (2)
D. If the observed rate law is Rate = k[NO]2[H2] , which of the two steps is the slow, rate determining step? (2)
VI. When 80.00 grams of a certain non-electrolyte are dissolved in 200.0 grams of water, the solution freezes at a temperature of 2.00°C . (Kf of water is 1.86°/m)
A. What is the molality of the solution? (2)
B. What is the molar mass of the solute? (3)
VII. Given the following data for the FIRST order decomposition of H2O2 at some temperature (6 points)
Time (seconds)Concentration (Molarity)
02.000
51.34
100.899
150.602
A. What is the rate constant for the reaction at this temperature? (include correct unit)
B. What is the half life of the H2O2 in seconds?
C. How long will it take, starting at time zero, for the molarity to reach a concentration of 0.200 molar?
VIII. H2(g) + CO2(g) ⇄ H2O(g) + CO(g)
When H2 is mixed with CO2 at 2000 K, equilibrium is achieved according to the equation above. In one experiment, the following equilibrium concentrations were measured. ( 9 points)
[H2] = 0.20 mol/L [CO2] = 0.30 mol/L [H2O] = [CO] = 0.55 mol/L
a) Using the equilibrium concentrations given above, calculate the value of Kc , the equilibrium constant for the reaction.
b) Determine Kp in terms of Kc for this system.
c) When the system is cooled from 2000 K to a lower temperature, 30.0 percent of the CO is converted back to CO2 . Calculate the value of Kc at this lower temperature.
d) In a different experiment, 0.50 mole of H2 is mixed with 0.50 mole of CO2 in a 3.0 liter reaction vessel at 2000 K. Calculate the equilibrium concentration, in moles per liter, of CO at this temperature. ( use the Kc you found in part a)