Page 87 - Demo

“Your Safer Source for Science” Electrochemistry
85
Electrochemistry
Electrodes
Mix and match the following electrodes, using the listed standard reduction potentials, to create your own electrochemical cell. All electrodes listed are strips except carbon rods and graphite pencil leads.
Catalog No.
Description
Dimensions
Reduction Half-Reaction
Standard Reduction Potential, E°
Price/Pkg.
A0178
Aluminum
6" x 1⁄2"
Al3+ + 3e¯ → Al(s)
–1.66 V
$ 5.95/10
B0231
Brass
6" x 1⁄2"
—
—
18.00/6
AP1817
Carbon, Graphite Pencil Leads
21⁄2" x 1⁄16" dia.
Inert Electrode*
2.50/15
C0410
Carbon, Rods
4" x 1⁄4" dia.
Inert Electrode*
11.40/6
C0182
Copper
6" x 1⁄2"
Cu2+ + 2e¯ → Cu(s)
+0.34 V
10.65/6
Cu2+ + e¯ → Cu+
+0.15 V
Cu+ + e¯ → Cu(s)
+0.52 V
I0058
Iron
6" x 1⁄2"
Fe3+ + 3e¯ → Fe(s)
–0.04 V
7.10/10
Fe3+ + e¯ → Fe2+
+0.77 V
Fe2+ + 2e¯ → Fe(s)
–0.45 V
L0065
Lead
6" x 1⁄2"
Pb2+ + 2e¯ → Pb(s)
–0.13 V
9.05/6
N0089
Nickel**
5" x 1⁄2"
Ni2+ + 2e¯ → Ni(s)
–0.26 V
18.45/6
S0270
Silver***
3" x 2"
Ag+ + e¯ → Ag(s)
+0.80 V
50.30
T0087
Tin
6" x 1⁄2"
Sn4+ + 2e¯ → Sn2+
+0.15 V
12.10/6
Sn2+ + 2e¯ → Sn(s)
–0.14 V
Z0024
Zinc
5" x 1⁄2"
Zn2+ + 2e¯ → Zn(s)
–0.76 V
9.00/10
*** Inert electrodes are electrodes made from a conducting, but unreactive, material. Thus, inert electrodes do not participate in the cell reaction. Instead, they provide a support surface for the reaction and a means for electron transfer.
*** Nickel electrode is nickel-plated steel and is magnetic.
*** Silver foil makes a great electrode. The 5-gram size is about 3" x 2" and can make
12–15 mini electrodes.
Hofmann Electrolysis Apparatus
One-way glass stopcocks conveniently located on the top of this high- quality apparatus allow for easy collection of gases during electrolysis experiments. The large center reservoir bulb will easily handle the liquid displacement from the two side columns and prevent any over- flow during your experiments. Electrodes and directions included. Requires ring stand, support clamp and a 9-V battery or DC power supply. Measures 41 x 17 cm.
ELECTROCHEMISTRY continued on next page.
Hofmann Electrolysis Apparatus AP5879
Catalog No.
Description
Price/Each
AP5879
Hofmann Electrolysis Apparatus
$169.55
Determine an Electrochemical Cell Potential
What causes an electric current to flow? There must be an electrical potential difference between two points in a circuit. Electrodes made of materials that–have differen+t standard reduction potentials can provide these two points and allow a curree¯nt to flow through aen¯ elec- trochemical cell.
If the net cell potential is positive, electrons will flow fZrnom the anode to the cathode spontane-
Electrode Ele ously. This is referred to as a voltaic cell. If the net cell potential is negative, an outside source
An electrochemical cell should be designed such that oxidation occurs at one of the electrodes (the anode) while reduction occurs at the other electrode (the cathode). You can mix and match
U-Shaped
electrodes, using their standard reduction potentials, to design your ownDeryliengcTturboechemical cell.
of electrical energy, such as a battery, is required for a current to flow. A non-spontaneous cell
potentials of two electrodes, the larger the voltage produced (voltaic cell) or needed to run the
cell (electrolytic cell).
For tips on how to use a porous cup in an electrochemical cell, see page 433.
like this is referred to as an electrolytic cell. The larger the difference between standard reduction
1.10 V
Salt Bridge
Cotton or Glass
Wool Plug
ZnSO4 Solution CuSO4 Solution
Anode
Cathode
1.10 V –+
Salt Bridge
U-Shaped Drying Tube
Cotton or Glass Wool Plug
Anode: Zn(s) Zn2+(aq) + 2e¯ EΥox Cathode: Cu2+(aq) + 2e¯ Cu(s) EΥred
Cu ctrode
Zn Electrode
= 0.76 V = 0.34 V
e¯
ZnSO4 Solution Anode
e¯
CuSO4 Solution Cathode
Cu Electrode
Net Cell Zn(s) + Cu2+(aq) Zn2+(aq) + Cu(s) EΥnet = 1.10 V
2+
Reaction:
Anode:
Cathode:
Cu2+(aq) + 2e¯
(aq) + 2e¯ Cu(s)
Zn(s) Zn
EΥox = 0.76 V EΥred = 0.34 V
Net Cell Reaction:
Zn(s) + Cu2+(aq)
Zn2+(aq) + Cu(s)
EΥnet = 1.10 V
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