Core Practical 10 : Construct electrochemical cells and measure their potentials

Overview

Procedure

What conditions does the ⦵ refer to?

• all solutions are 1.0moldm-3 with respect to the ion being tested

• If gases are used, pressure is 100kPa

• Temperature of 298K

Why are lower concentrations of silver nitrate solution used than should be?

• too expensive

• Particularly dangerous to handle as 1.0moldm-3 silver nitrate is oxidising and corrosive

The cell potentials for the cells you set up may be slightly different to theoretical values. Give a reason for this.

• concentrations of solutions may not be exactly 1.0moldm-3, particularly for solutions of Ag+ as using 1 molar of Ag+ would be very expensive (and also high concentrations of silver nitrate solution is oxidising and corrosive so dangerous to handle)

• Concentration of solution affects the value of Ecell, so having concentrations different to 1.0moldm-3 would cause the system to move away from standard conditions and would cause results to be different to theoretical ones

[Mg2+(aq)IMg(s)] can also be used as a half-cell. Describe a problem that might be observed with this system

• A layer of MgO may form on the surface of the metal, which would prevent it from becoming oxidised and losing electrons (sand paper should remove this)

• the Mg will also react slowly with water