Chemistry 104,  Hour Exam #1            Name ____________________________

October 10, 1996                        Lab Section _______________________


I.   (12 pts)  Clearly draw three different isomers with the molecular formula C7H12 and
     provide the IUPAC name for each.

     (A)



     (B)



     (C)



II.  (4 pts @) Define briefly and concisely:

     (A)  Second-order reaction



     (B)  Br nsted-Lowry base



     (C)  Transition state (activated complex)



     (D)  Aromatic compound



III. (6 pts)  Methylamine (liq), CH3NH2, can be a solvent and behaves in many ways
     like water.  Reason by analogy to water and show with appropriate chemical
     equations what is the strongest acid that can exist in CH3NH2, and, secondly,
     write an equation for a reaction that will increase the acidity of a methylamine
     solution.  



page two      Hour Exam #1, C104

IV.  (6 pts @)  Balance the following redox reactions.

               (a)  H3PO2 + Cr2O72-     H3PO4 + Cr3+




               (b)  I2 + HNO3     HIO3 + NO2 




V.   The decomposition of dimethyl ether at 504 øC is a first-order reaction with a half-
     life of 27 min.

          (CH3)2O(g)     CH4(g)  +  H2(g)  +  CO(g)

     (A)  (5 pts)  What will be the partial pressure of (CH3)2O(g) after 1.00 h, if its initial
          partial pressure was 626 mmHg?




     (B)  (5 pts)  What will be the total gas pressure after 1.00 h?




VI.  (12 pts)  For the following endothermic reaction ( H rxn = 128 kJ):

          2NaHCO3(s)     Na2CO3(s)  +  H2O(g)  +  CO2(g)

     state the effects (increase, decrease, no change) on (1) the number of moles of,
     and (2) the concentration of sodium carbonate, Na2CO3, at equilibrium in a sealed
     container.

     (A)  removing CO2(g)          (1)

                              (2)
     (B)  raising the temperature  (1)

                              (2)       
     (C)  adding NaHCO3(s)         (1)

                              (2)

page three - Hour Exam #1, C104

VII. (8 pts)  Calculate the pH of a solution of pyridine (C5H5N) that has 1.25 g in 125 mL
     of water solution.  Pyridine is an organic base.  Kb = 1.5 x 10-9.






VIII.     (12 pts)  The reaction PCl5(g)     PCl3(g)  +  Cl2(g) has the equilibrium constant
          value Kc = 0.24 at 300 øC.  If the concentrations of the three gases are (in the
          order shown) 2.6, 0.5 and 0.5 mol/L, (A) show whether the system is at
          equilibrium, (B) determine which direction the reaction will react if it is not at
          equilibrium, and (C) calculate the equilibrium concentrations.

     (A)


     (B)


     (C)




IX.  (12 pts)  The rate law for the substitution of NH3 for H2O in the reaction

     Ni(H2O)62+(aq)  +  NH3(aq)     Ni(H2O)5(NH3)2+(aq)  +  H2O( )

     is first order in Ni(H2O)62+ and zero order in ammonia.  Write the experimental rate
     law and determine whether the following mechanism is consistent with it?  

     Ni(H2O)62+  +  NH3     Ni(H2O)6(NH3)2+                 (slow)

     Ni(H2O)6(NH3)2+     Ni(H2O)5(NH3)2+  +  H2O               (fast)

     If you disagree with the mechansism shown, write a better one.






page four - C104 hour exam



EXTRA CREDIT  (2pts each)


(1)  Name the authors of your textbook.



(2)  In the "purple-bottle" experiment, describe the relationship between the number of
     shakes of the flask and the intensity of the purple color?



(3)  Who is Freidrich August Kekul‚ (1829 - 1896)?



(4)  Give an example of a zero-order reaction.



(5)  Draw the structure of pyridine (see question VII).