TEST  3         

Show your work on calculations, and give
answers to the correct number of significant figures. 
You may use atomic weight values rounded to the
nearest 0.1 amu.

Points

1.   You dissolve 25.0 g of formic acid (HCOOH) and 25.0 g of sodium
     formate (NaHCOO) in enough water to make a solution that has a
     volume of 500.0 mL.  

(8)  (a)   Calculate the pH of the solution.

















(8)  (b)   You add 250.0 mL of 0.350 M NaOH to this solution.  What is
           the pH after the NaOH addition?

2.   You have 250.0 mL of a 0.550 M solution of ammonia. 

(8)  (a)   Calculate the pH of the solution.

















(8)  (b)   Calculate the pH after adding 250.0 mL of 0.330 M HCl to the
           solution in part (a).

















(8)  (c)   Calculate the pH after adding 500.0 mL of 0.33 M HCl to the
           solution in part (a).


3.   Calculate the solubility in grams of PbCl2 in:

(8)  (a) one liter of water.









(8)  (b) one liter of 1.5 M HCl solution.












(8)4.What is the pH of a saturated solution of Zn(OH)2?















(8)5.You add sodium hydroxide dropwise to a solution of 0.200 M ZnCl2. 
     At what pH will Zn(OH)2 begin to precipitate?








(8)6.For the following reaction, the initial rate of appearance of NH3
     (delta NH3/delta t) was determined to be  +3.66 x 10-3 Ms-1.  

           N2(g)   +    3 H2(g)  ---->   2 NH3(g)


     What is the rate of the reaction expressed as:

     delta N2/delta t?  ___________

     delta H2/delta t?  ___________


7.   The rate law for the following reaction is first order in H2 and
     second order in NO.

           2 NO(g)   +   2 H2(g)  ---->   N2(g)   +    2 H2O(g)

(3)  (a)   Write the rate law.




(3)  (b)  What are the units for k?




(3)  (c)   Does this reaction represent an elementary step?  How do you
           know?



(5)8.The decomposition of urea in acid solution proceeds as a first
     order reaction.  The half life of urea in an acidified urine sample
     was found to be 6 hours at 25oC.  If you acidified a urine sample
     that was 0.500 M in urea, what would be the urea concentration
     after storage for one day (24 hours)?







(6)9.Write the Arrhenius equation, and explain what is meant by each
     term.