EMF of an electrochemical cell

A/L Chemistry · G.C.E. Advanced Level · Grades 12–13

Aim

To measure the EMF of cells made from metal pairs and compare with standard electrode potentials.

Apparatus

• Zn, Cu, Fe, Mg and Ag electrodes
• 1.0 mol dm⁻³ salt solutions and a salt bridge
• High-resistance voltmeter

Method

1. Dip each metal of a pair into its own salt solution.
2. Join the solutions with a salt bridge.
3. Connect the voltmeter and read the EMF.
4. Compare with E°cell = E°cathode − E°anode.

Conclusion

The measured EMF matches the difference in standard potentials (E°cathode − E°anode). The metal with the lower E° is the anode (oxidised).