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E-mail me the answer to the following questions.  If the question is a calculation, send the answer and a description of how you arrived at the answer (you need not try to type in math).  See the Instructions for Problem Sets. (Use the "Back" button or menu command on your browser to return to this page.) 

1.  Answer Question 7 on the 1993 AP examination. (An example of an AP essay question.) 

2.  Answer Question 2 on the 1992 AP examination. (An example of an AP  free response problem.) 

3.  Tarnished silver is coated with Ag2S.  The tarnish can be removed by placing the silverware in an aluminum pan and covering it with a solution of an inert electrolyte such as NaCl.  Explain the electrochemical basis for this procedure. 

4.  What features determine the voltage of a battery?  What determines the number of coulombs that a battery can deliver? 

5.  Calculate the potential of each of the following cells at 25 oC with reactants and products having the conditions indicated.  If no pressure or concentration is indicated for a species, assume unit activity (1 M concentrations, 1 atm. pressure, pure solids).  

  1. Mn(s) + 2 Ag+(0.0100 M) -> Mn2+(0.0100 M) + 2 Ag(s)
  2. MnO4-(0.155 M) + 8 H3O+(1.200 M) + 5 Au(s) -> Mn2+(0.0100 M) + 12 H2O(l) + 5 Au+(0.0200 M)
  3. Cr2O72-(0.403 M)  +  5 H3O+(0.252 M)  + 3 HNO2(0.100)    ->    2 Cr3+(0.000504 M) + 3 NO3-(0.00102 M) + 9 H2O(l)
6..  Calculate the equilibrium constant of each reaction using data from a table of standard reduction potentials. 
  1. Cr2O72- + 3 Fe(s) + 14 H3O+(aq) -> 2 Cr3+(aq) + 3 Fe2+(aq) + 21 H2O(l)
  2. 2 Br- + F2 -> 2 F- + Br2
7.  Chlorine gas is an important industrial chemical produced by electrolysis.  How many moles of electrons are required to prepare 1.000 metric ton (1000. kg) of chlorine gas by electrolysis of an aqueous solution of sodium chloride?   

      2 NaCl(aq) + 2 H2O(l) -> 2 NaOH(aq) + H2(g) + Cl2(g) 

How many faradays?  How many coulombs?  Assume that the efficiency of the electrochemical cell is 100%; that is, every electron involved results in the production of a chlorine atom.  (In an actual commercial cell the efficiency is about 65%.) 

8.   A current of 9.0 A flowed for 45 min through water containing a small quantity of sodium hydroxide.  Determine the volume of gas (in liters) formed at the anode at 27.0oC and 750 torr of pressure under the following sets of conditions.   

  1. Assume the gas contains no water vapor.
  2. The gas is saturated with water vapor at 27.0oC.
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