RP 8 - Measuring EMF of an electrochemical cell

Question 1

What is an electrochemical cell?

Answer 1

• Two different half cells are connected by salt bridge with their electrodes connected to a volt meter. This allows the flow of electron.
• 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 or ion/ion
• Each half cell will contain the chemical species from 1/2 of a redox reaction

Question 3

What is a salt bridge?

Answer 3

• A salt bridge allows the transfer of ions
• It is typically a concentrated solution of an electrolyte for example potassium nitrate that doesn’t react with either half cell solution

Question 4

Why may a graphite or platinum electrode be used?

Answer 4

They are very unreactive and will not react with the half cell solutions and will not affect the vault meter readings

Question 5

How do you measure comparative electrode potential of different metals?

Answer 5

1) File a piece of copper using emery paper and connect it to the positive volt terminal.
2) Cut a piece of filter paper saturate with potassium nitrate 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 and record the voltmeter value.
5) Repeat with different metals and record the results in a table.

Question 6

Why do you need to file away the outer layer of the metal?

Answer 6

It removes the oxide layer on the outside of the metal