Chemistry 114
Third Hour Exam
Name:____________
This test contains a total of 105 points - your grade will be based on 100 points -so you can
miss 5 points for free
1. (10 points) What are the proper units for: (assume concentrations in moles/liter, and time is in
seconds)
A. The rate of a chemical reaction
B. The rate constant for a zero order rate law
C. The rate constant for a second order rate law
D. An acid dissociation constant, Ka
E. Kw
2. In a kinetic analysis of the reaction
A+B6C
The following results were obtained
[A] (M)
[B] (M)
Initial rate (mol/l@min)
.1
.3
1.424x10-3
.25
.3
8.906x10-3
.25
.5
14.844x10-3
A. (5 points) What is the order for this reaction with respect to A
B. (5 points) What is the order for this reaction with respect to B
C. (5 points) What is the rate constant for this reaction
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3. (5 points) A first order reaction has a half-life of 15 seconds. What is the rate constant for
this reaction?
4A. (2 points) What is the integrated rate law for a second order reaction.
B. (4 points) If the initial concentration of the reactant in a second order reaction is .25M, and
the rate of the reaction is .025 mol/l@sec, what is the concentration of the reactant after 10 seconds
C. (4 points) What is the half-life of the above reaction when the concentration of the reactant is
.5M ?
5. (10 points) What is meant by the term ‘activation energy’ and what plot do we use to
determine its value?
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6A.(3 points) What is the equilibrium expression for the following reaction:
Cr2O72- + 14 H+ + 6Cu1+W 2Cr3+ + 7H2O + 6Cu2+
B. (2 points) What are the units for the above equilibrium constant?
7. ( 5 points) I have a gas phase reaction:
2A(g) + 3B(g) W C (g)
If the K based on concentration for the above reaction is 5.076 l4/mol4 at 25oC, what is
Kp?
8. (15 points) BaF2 is a slightly soluble salt. The reaction BaF2(s) W Ba2+(aq) + 2F-(aq) has a K of
2.4 x10-5 mol3/l3. If I have a 0.001 M solution of Ba2+ what is the minimum concentration of Fthat is needed to start the formation of a BaF2 precipitate
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9. I have a 100 mL solution that is .0001 M Ag+ and a second 100 ml solution that is .0001M Cl-.
When I mix these solutions together the initial concentration of the two ions in the solution will be
.00005M Ag+ and .00005M Cl-. However, I know that AgCl is not very soluble, and I have just
looked up the Ksp of AgCl, and found that it is 1.6x10-10 mol2/l2
A. ( 5 points) Use a Q calculation to find out if a precipitate will form.
B. (10 points) Calculate the concentrations of Ag+ and Cl- after the system comes to
equilibrium
10. A (5 points) Lemon juice has a pH of about 2.5, what [H+] does this correspond to?
B ( 5 points) Household ammonia has a pH of 12, what [H+] does this correspond to?
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11. (5 points) What is the pH of a .000456 M KOH solution?
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