Required practical 3 - Measure the EMF of an electrochemical cell

Describe the method for this practical

Clean the zinc and copper foils with emery before use. Degrease the metal using some cotton wool and propanone. • Place the copper strip into a 100 cm3beaker with about 50 cm3of 1 moldm-3CuSO4solution. • Placethezinc stripinto a 100 cm3 beaker with about 50 cm3of 1 moldm-3ZnSO4solution. • Use a strip of filter paper soaked in saturated potassium nitrate solution for the salt bridge • Connect the Cu(s)|Cu2+(aq) and Zn(s)|Zn2+(aq) half cells by connecting the metals using the crocodile clips and leads provided to the voltmeter

What is the salt bridge and why is it used?

The salt bridge is used to connect up the circuit. The free moving ionsconduct the charge. Asalt bridge is usually made from a piece of filter paper (or material) soaked in a salt solution, usuallypotassium nitrate. It can also be a glass U tube containing a salt solution plugged with cotton wool. Thesalt should beunreactive with theelectrodesand electrode solutions. E.g. potassium chloride would not be suitable for copper systems because chloride ions can form complexes with copper ions. Awire is not used because the metal wire would set up its own electrode system with the solutions

What do you do if one or both of the half cells aren't a conducting metal/solid?

use a platinum electrode

What are the three conditions the half cells need to be under?

298 k

1 atm

1 mol dm-3

Why is a platinum electrode used?

Inert and conducts electricity.