Experiment 3: Constructing a zinc/ iron cell

Experiment 2: Constructing a zinc/ copper cell

· A zinc/ copper cell was set up as it was shown in the figure in laboratory manual.

· The zinc and copper were cleaned with emery paper before use.

· 1.0 M zinc sulphate and copper sulphate solutions were used for the electrolytes and a strip of filter paper was soaked in saturated potassium nitrate for the salt bridge.

· The polarity of the electrodes was predicted then the e.m.f of the cell was measured using a high resistance voltmeter.

· The cell e.m.f was recorded.

· Bearing in mind the relative tendencies of zinc, iron and copper to lose electrons, it was predicted whether the e.m.f of the zinc/iron cell would be less than or greater than that of zinc/ copper.

Experiment 3: Constructing a zinc/ iron cell

· A zinc/ iron cell was set up using a similar arrangement to the previous one with a Fe/Fe²⁺ half-cell instead of a copper one.

· The copper half-cell was kept for a later experiment.

· A clean iron nail was used for the electrode and an acidified 1.0 M iron (II) sulphate solution was used as the electrolyte.

· A fresh salt bridge was used.

· The polarity of the cell was predicted before measuring the e.m.f

· The E⁰_cell was recorded.

· Assuming each half-cell in a cell makes a fixed, independent contribution to E⁰_cell by using previous results, it was predicted the E⁰_cell of an iron/ copper cell.

· An equation for the cell reaction was wrote.