Chemistry 104,  Hour Exam #2            Name ____________________________

November 14, 1996                       Lab Section _______________________


I.   (4 pts @) Define briefly and concisely (give examples where appropriate):

     (A)  Multi-center Bonding



     (B)  Acid Anhydride



     (C)  Spontaneous Reaction



     (D)  The Second-Law of Thermodynamics (no silly paraphrasing, please)



II.  (4 pts @) For the following processes state whether the entropy change will be
     positive, negative or very nearly unchanged, and explain your answer in a
     sentence:

     a.   Putting cream in your coffee.


     b.   Sublimation (e.g., when dry ice disappears).


     c.   Forming water from its elements at 500øC.


     d.   Studying for this exam.


III. (7 pts)  Outline briefly the purification process for bauxite (hydrated aluminum
     oxide) in which silicon and iron containing impurities are removed.  Show how
     amphoteric behavior is important.





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IV.  (12 pts)  A 700 mL solution is prepared that contains 8.00 grams of propylamine
     (C3H7NH2 - Kb = 3.5 x 10-4) and 14.00 grams of propylamine hydrochloride
     (C3H7NH3Cl).  What is the pH of this solution?  What is the new pH of the solution
     after 25 mL of a 0.125 M solution of NaOH is added?











V.    pts  Write equations that show whether the aqueous solutions of the following
     salts will  have pH values greater than 7, less than 7, equal to 7 or indeterminant.

     a.   NaHCO3.


     b.   (NH4)2SO4.


     c.   Rb acetate


     d.   Al(NO3)3.


VI.  (8 pys)  What [CrO42-] must be present in 0.00176 M AgNO3 to just cause the
     precipitation of Ag2CrO4 to begin?  Ksp(Ag2CrO4) = 2.4 x 10-12?












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VII. (7 pts)  Using chemical equations and words, give an example of the "common-ion
     effect" in operation.







VIII.     (4 pts @)  Would you expect each of the following reactions to be spontaneous at
          low temperatures, high temperatures, all temperatures, or not at all?  (Briefly
          explain your choices.)

     a.   H2O(g) + 1/2 O2(g)    H2O2   Hø = +105.5 kJ/mol



     b.   CH4(g) + 2 O2(g)     CO2(g) + 2 H2O(g)   Hø = -802.5 kJ/mol



IX.  (8 pts)  For the sublimation of naphthalene at 298 K:  Sø= 99.7J/K mol;  Hø=
     73.6kJ/mol.  Calculate the partial pressure of naphthalene vapor in equilibrium with
     solid naphthalene.  











X.   (10 pts)  Write a very brief essay (about two paragraphs starting here and finishing
     on the back of your exam) in which you comment on the quotation from Max
     Planck "It is impossible in any way to diminish the entropy of a system of bodies
     without thereby leaving behind changes in other bodies."


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EXTRA CREDIT  (2pts each)


(1)  Name any of the three people who won the Nobel Prize in chemistry this year.



(2)  What did they do to merit the prize?



(3)  Who was J. Willard Gibbs?



(4)  Give the formula for borax.



(5)  What is deceptive about writing a solubility equilibium for a salt MA2 as:

          MA2       M2+(aq)  +  2A-(aq)