Rossita Radzak SASER

VOLTAGE CELLS

Figure Voltaic cell using zinc and copper plate

Observation Explanation Galvanometer needle deflects Electric current is produced due to the flow of

electrons Zinc electrode dissolves/ ionized / become thinner.

Zinc ionises and becomes Zn2+ ions

Bubbles of gas evolve at copper electrode. Hydrogen gas is produced. 1. Zinc is higher than copper in the Electrochemical Series. Hence a zinc atom releases 2 electrons to form zinc ion more easily than copper atom. Zinc electrode acts as the negative terminal. Zn Zn2+ + 2e ( oxidation process) 2. The electrons that are released flow through the external circuit towards the copper electrode which acts as the positive terminal. 3. At copper electrode, the electrons are accepted by the hydrogen ions, H+.

2H+ + 2e H2 (reduction process)

Zinc electrode

Copper electrode Dilute sulphuric acid

Metal K Na Ca Mg Al Zn Fe Sn Pb Cu Ag

Ease of releasing electrons increases

Figure The Electrochemical Series

1. A simple voltaic cell consists of two different

metals immersed into an electrolyte.

2. Voltaic cell converts chemical energy to electrical

energy.

3. The more electopositve metal becomes the negative

terminal from which electrons flow.

4. The further apart the metals are in the

Electrochemical Series, the higher the voltage of the

cell.