NCSU – Dept. of Chemistry – Lecture Demonstrations
Electrochemistry
Galvanic Cell (Zn2+/Zn with Cu2+/Cu)
Description: A galvanic cell is constructed using Zn2+/Zn and Cu2+/Cu couples
with a NaCl salt bridge.
Materials:
1 M CuSO4
1 M ZnSO4
Zn and Cu strips
Voltmeter
Connecting wires
Salt bridge strips
Procedure:
For large lecture halls, project demonstration using a document camera.
1. Pour 1 M CuSO4 and 1 M ZnSO4 solutions in separate containers (or use
setup in Dabney 114). Place the Zn electrode in the ZnSO4 solution and
the Cu electrode in the CuSO4 solution.
2. Connect the black wire (anode) to the Zn electrode and the red wire
(cathode) to the Cu electrode. The voltmeter will not show any reading
until the circuit is completed by the salt bridge (filter paper strip soaked in
saturated NaCl solution). Make sure the salt bridge makes contact with
both solutions.
Discussion:
Due to their respective reduction potentials, a spontaneous redox process occurs
when the zinc electrode is connected to the negative terminal and the copper
electrode is connected to the positive terminal of the voltmeter.
The
spontaneous flow of electrons from anode to cathode generates a current with a
voltage near the theoretical Eocell for these couples (1.10 V).
Anode
Cathode
Zn → Zn2+ + 2 e1Cu2+ + 2 e1- → Cu
Eored (V)
- 0.76
+ 0.34
Safety: Wear proper protective equipment including gloves and safety glasses
when preparing and performing this demonstration.
NCSU – Dept. of Chemistry – Lecture Demonstrations
Electrochemistry
Disposal: Copper and zinc solutions can be reused as long as no contamination
occurred. Electrodes should be rinsed, dried and cleaned by scrubbing with steel
wool.
References:
Shakhashiri, B. Z. In Chemical Demonstrations: A Handbook for Teachers of
Chemistry; The University of Wisconsin Press: 1992; Vol. 4, p 101-106.
Video :
http://www.youtube.com/watch?v=A0VUsoeT9aM (animation)
http://www.youtube.com/watch?v=0oSqPDD2rMA (animation)