RP8: Measuring EMF of an electrochemical cell

Question 1

What is an electrochemical cell?

Answer 1

Two different half-cells are connected by a salt bridge, with their electrodes connected to a voltmeter (measures EMF/cell potential). This allows the flow of electrons.

The electrical energy generated is from chemical redox reactions.

Question 2

What does a half-cell consist of?

Answer 2

Half-cells are usually metal/metal ion (metal electrode in the metal ion solution) or ion/ion (ions that are the same element but with different oxidation states, in solution).

Each half-cell will contain the chemical species from one half of a redox reaction (redox half equation).

Question 3

What is a salt bridge?

Answer 3

Salt bridge allows the transfer of ions.

Question 4

Why may a graphite or platinum electrode be used?

Answer 4

They are very unreactive.

Question 5

How do you measure comparative electrode potentials of different metals?

Answer 5

1. File a piece of copper using emery paper and connect it to the positive voltmeter terminal
2. Cut a piece of filter paper, saturate with KNO3 solution and place on top of the copper
3. Connect the voltmeter to another piece of metal
4. Hold the metal against the filter paper