AP Chemistry - Electrochemistry Worksheet #6

1.  An electrochemical cell consists of a chromium electrode in a 1.0 mol/L solution of Cr(NO3)3, a silver electrode in a 1.0 mol/L solution of AgNO3 and a salt bridge.
The spontaneous cell reaction is:

        Cr(s) + 3 Ag+(aq) ---> Cr3+(aq) + 3 Ag(s)

If a 2.0 mol/L solution of NaCl is added to the beaker containing AgNO3
a) the chromium ion concentration will increase.
b) the reading on the voltmeter will decrease.
c) the reading on the voltmeter will increase.
d) the reading on the voltmeter will remain unchanged.
 

2. The cell reaction during the discharge of a lead storage battery is.

    Pb(s) + PbO2(s) + 4 H1+(aq) + 2 SO42-(aq)   -->   2 PbSO4(s) + 2 H2O

The standard cell potential is 2.05 V.  What is the correct form of the Nernst equation for this reaction?
 

3. The cell reaction

    NiO2(s) + 4 H+(aq) + 2 Ag(s) --->  Ni2+(aq) + 2 H2O + 2 Ag+(aq)

has Eocell = 2.48 V.  What will be the cell potential at a pH of 6.00 when the concentrations of Ni2+ and Ag+ are each 0.10 M?
 

4. Eocell = 0.135 V for the reaction

    3 I2(s) + 5 Cr2O72-(aq) + 34 H+(aq) -----> 6 IO3-(aq) + 10 Cr3+(aq) + 17 H2O

What is Ecell if [Cr2O72-] = 0.10 M, [H1+] = 0.010 M,
                         [IO31-] = 0.0010 M, and [Cr3+] = 0.00010 M?

 

5. A cell was set up having the following reaction.

    Mg(s) + Cd2+(aq) ---->  Mg2+(aq) + Cd(s) Eocell = 1.97 V

The magnesium electrode was dipping into a 1.00 M solution of MgSO4 and the cadmium was dipping into a solution of unknown Cd2+ concentration.  The potential of  the cell was measured to be 1.67 V.  What was the unknown Cd2+ concentration?
 

6. A galvanic cell was set up having the following half-reactions.

        Fe2+(aq) + 2 e- --->  Fe(s)     EoFe2+ = -0.440 V
        Cu2+(aq) + 2 e- --->  Cu(s)    EoCu2+ = +0.337 V

The copper half-cell contained 100 mL of 1.00 M CuSO4.  The iron half-cell contained 50.0 mL of 0.100 M FeSO4. To the iron half-cell was added 50.0 mL of 0.500 M NaOH solution. The mixture was stirred and the cell potential  was measured to be 1.175 V. Calculate the value of Ksp for Fe(OH)2.
 

7. A cell employs the following half-reactions.

        Ni2+(aq) + 2 e- --->  Ni(s)    EoNi2+ = -0.25 V
        Cr3+(aq) + 3 e- --->  Cr(s)    EoCr3+ = -0.74 V

Calculate the potential if [Ni2+] = 1.0 x 10-4 and [Cr3+] = 2.0 x 10-3 M.

8. In a certain zinc-copper cell,

        Zn(s) + Cu2+(aq)   --->  Zn2+(aq) + Cu(s)

The ion concentrations are [Cu2+] = 0.0100 M and [Zn2+] = 1.0 M.  What is the cell potential?  The standard potential is 1.10 V.

9. A galvanic cell was constructed by connecting a nickel electrode that was dipping into 1.20 M NiSO4 solution to a chromium electrode that was dipping into a solution containing Cr3+ at an unknown concentration.  The potential of the cell was measured to be 0.55 V, with the chromium serving as the anode.   What was the concentration of Cr3+ in the solution of unknown concentration?

10.  Suppose that a galvanic cell were set up having the net cell reaction

        Zn(s) + 2 Ag1+(aq) ---> Zn2+(aq) + 2 Ag(s)

The Ag1+ and Zn2+ concentrations in their respective half cells initially are 1.00 M, and each half-cell contains 100 mL of electrolyte solution.  If this cell delivers current at a constant rate of 0.10 A, what will the cell potential be after 10.00 hr?