A voltaic cell converts chemical energy to electrical energy using two different metals immersed in an electrolyte. The more electropositive metal becomes the negative terminal, releasing electrons that flow through an external circuit to the other metal, which acts as the positive terminal. For example, a zinc-copper voltaic cell uses zinc and copper plates in a dilute sulfuric acid electrolyte, with zinc dissolving as ions and electrons flowing to the copper where they combine with hydrogen ions to produce bubbles of hydrogen gas. Zinc is higher than copper in the electrochemical series, so it more easily releases electrons to power the flow of current.

1. Rossita Radzak SASER
VOLTAGE CELLS
1. A simple voltaic cell consists of two different Metal
K
metals immersed into an electrolyte. Na
Ca
2. Voltaic cell converts chemical energy to electrical
Mg
energy. Al
Zn
3. The more electopositve metal becomes the negative Fe Ease of
Sn releasing
terminal from which electrons flow. Pb electrons
4. The further apart the metals are in the Cu increases
Ag
Electrochemical Series, the higher the voltage of the
cell. Figure The Electrochemical
Series
Copper electrode
Zinc electrode
Dilute sulphuric acid
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 Zinc ionises and becomes Zn2+ ions
thinner.
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)