CH302H - Principles of Chemistry II: Honors
Spring 2016, Unique 49420


Homework, Week 11


Homework, week 11
Answer key

1.  A 10 mL solution containing 3.0 x 10-5 M Cu2+ is used in an electrolytic cell for the reduction of Cu2+ to Cu(s) at an electrode.  The cell is run at a constant current of 3.0 mA.

a) Is the copper deposited on the anode or cathode of this cell?

b) How long must the electrolysis run to reduce all of the Cu2+?

c) If your solution was contaminated with a metal that was easier to reduce than copper, would your calculation for the amount of copper in the solution based on this electrolysis give you a value that was too low or too high?  Justify your answer.

2. Given the following electrochemical cell:

Ag | AgI | K+ (0.0030 M), I- (0.0030 M) || Ag+ (0.0010 M), NO3- (0.001 M) | Ag

(i.e. the electrode on the left hand side of the cell is a Ag wire on which AgI is deposited).

a) Write the half cell reactions (expressed as reductions) and their values of E0.

b) Write the overall chemical reaction taking place in this cell.

c) What is E0cell?  If you cannot find a reduction potential for one of your half reactions in your textbook, it is -0.152 V, but make sure you know which reaction is described by this potential.

d) What is the anode in the cell?

e) Was is DG0 for this reaction?

f) Which chemical species is serving as the reducing agent in this reaction?

3.  A piece of Cu metal is put into a solution containing 1.0 M HCl and maintained under a constant pressure of 1.0 atm H2(g).  Will the Cu dissolve?

4.  The same experiment as problem 3 is now run with a solution of 1.0 M HNO3. Will the Cu dissolve?

5.  Is potassium permanganate (KMnO4) a good oxidizing agent, reducing agent, or neither?  Justify your answer.

6.  Methane (CH4) gas is a convenient and relatively clean-burning fuel, but it is difficult to store in gas form.  There is therefore great interest in converting CH4 to methanol (CH3OH), which is a liquid at room temperature and much easier to store and transport.  This is done by dissolving methane in and acidic aqueous solution. 

a) Is this a redox reaction? (This question implies that you should write out the balanced reaction.)

b) If the products includes H2(g) as well as methanol, is this a redox reaction?

7.  Use information from the table of standard reduction potentials in your textbook to determine the Ksp for Hg2Cl2(s).