Cliffs AP Chemistry, 3rd Edition

Next, the student used three different combinations of metals for both anodes and cathodes and
measured the potential difference. The results are presented in Table 5.

Table 5

Anode Cathode Measured Potential Difference

Fe Cu 0.50

Mg Pb 1.00

Pb Cu 0.51

A 0.0100 M Cu(NO 3 ) 2 solution was then made up and used in the Cu2+| Cu half-cell. The
[Zn2+(aq)] was kept at 1.0 M in the Zn | Zn2+half-cell. The voltage was then determined and mea-
sured as 1.01 volts.

The student then added 10. mL of 1.0 M NaCl solution to an empty beaker. He then added one
drop of 1.0 M AgNO 3 to the beaker and stirred well. Since there is an abundance of Cl−in the
beaker, and the amount of NaCl (10. mL) is magnitudes greater than the one drop of 1.0 M
AgNO 3 , it can be assumed that most of the Ag+(aq)will combine with the Cl–(aq)and that the con-
centration of the Cl–(aq)will remain essentially 1.0 M. A silver metal electrode was immersed in
this solution and connected through the salt bridge to the Zn | Zn2+half-cell. The potential dif-
ference was measured as 0.91 volts.

And finally, the same procedure was followed as above, but instead of obtaining an unknown
concentration of silver ion, the student prepared a solution containing 2 drops of 1.00 M
Cu(NO 3 ) 2 in 10. mL of 6.00 M NH 3. The student determined that it took 20. drops to equal 1
mL. This solution was then added to the cell containing the copper electrode. The voltage was
read as 0.56 V. The cell can be represented as:

Zn(s)| Zn2+(aq)(1.00 M) || Cu2+(aq)(? M) | Cu(s)

Analysis:

1. Examine Table 1. Write balanced net ionic equations where reactions occurred and iden-
   tify the oxidizing agent (OA) and the reducing agent (RA) for each equation.
   Cu^22 +()aq +Mg()ss"Cu()+Mg()aq+ OA = Cu2+; RA = Mg(s)
   Cu^22 +()aq +Pb()ss"Cu()+Pb()aq+ OA = Cu2+; RA = Pb(s)
   Cu^22 +()aq +Zn()ss"Cu()+Zn()aq+ OA = Cu2+; RA = Zn(s)
   Pb^22 +()aq +Mg()ss"Pb()+Mg()aq+ OA = Pb2+; RA = Mg(s)


2. Referring to Table 1, list the metals studied in order of increasing ease of oxidation.
   Copper < Lead < Magnesium


3. Referring to Table 1, list the metallic ions studied in order of increasing ease of reduction.
   Mg2+(aq) < Pb2+(aq) < Cu2+(aq)

Part III: AP Chemistry Laboratory Experiments