Arkansas State University 
Department of Chemistry
and Physics
CHEM1013
Exam 4
(Note: only the questions are listed, spaces have been removed for brevity)

SHOW WORK ON ALL PROBLEMS

1.  Circle the combinations which could serve as buffer solutions.        (10 points)
 
a)  HCl / NaCl  b) NH3 / (NH4)2SO4
   
c) H2O / NaOH  d)  HOCl / KOCl
   
e) H3PO4/ KH2PO4

2. Calculate the pH of a buffer solution made from 0.40 M acetic acid and 0.60 M sodium acetate.  Ka = 1.8 x 10-5   (10 points)

3. Calculate the pH of a buffer solution made from 0.60 M acetic acid and 0.60 M sodium acetate after the addition of 0.08 mol of NaOH.  Assume no change in volume. Ka = 1.8 x 10-5  (10 points)

4.  What would be the buffer range for an acid if its Ka = 1.6 x 10-5 ?    (4 points)

5.  Determine a) the order of each reactant, b) the order of the reaction, c) writ the rate law and d) calculate the rate constant, k, for the following data:  (place answers in spaces beow.  15 points)
 
Reaction
[A]
[B]
rate
1.
0.20 M
0.10 M
3.50 x 10-3 
2.
0.40 
0.10 
7.00 x 10-3 
3.
0.20 
0.20 
7.00 x 10-3

Order of A                                  Order of B                .

Reaction Order                             Rate Law                                                      .

k =                                                      .

6a.   The decomposition of AB3 is first order with a k = 1.5 x 10-5 s-1 at 25oC.  If the initial concentration is 0. 50 M, what is the concentration after 2 min?  (6 points)

6b.  What is the half-life for the reaction in 6a?  (4 points)

7.  Draw the potential energy vs. rection coordinate plot for the exothermic reaction of
2 A ------>  C  +  D.  Label all parts.   (6 points)

8.  Write the Arrhenius equation.   (5 points)

9.  Fill in the blank.   (5 points)

a)  List the three types of catalysts                               ,                              ,                            .

b)  Reactants in enzyme reactions are called                                              .

c)  The Haber Process is used to                                                 .

10.  Write the rate expression in terms of D[reactant]/ Dt and D[product]/ Dt for the reaction:   (6 points)

NaOH   +   CO2   ------>   NaHCO3

11.  Define Collision theory.   (4 points)

12.  Define rate determining step.   (4 points)

13.  Define catalyst.   (4 points)

14.  Given the rections below, answer the following questions.   (7 points)

rxn 1:       2 NO2   -------->    N2O4

rxn 2:    N2O4   +   CO  ------->   NO   +    CO2    +   NO2

a)  what are the individual steps called?

b) what compound is the intermediate in this mechanism?

c)  write the overall reaction