Primary cell

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Galvanic (Voltaic) cell

A galvanic cell is the supply of direct current (DC) consists of two half-cells. These two half-cells are physically separated. Each half-cell consists of an electrode that is conductive metal or graphite strip in contact with an electrolyte solution. Those solutions are joined by a salt bridge containing an electrolytic solution like Potassium Nitrate (KNO3). The salt bridge completes the circuit and permits ions to travels between two half-cell.

The electrode where the oxidation reaction (Loss of electrons) takes place is termed the anode. As electrons are released by oxidation, the terminal of the anode is marked negative (-). The electrode where reduction reaction takes place is termed the cathode. As a result of the cathode accepting electrons the reduction reaction (Gain of electrons) is presented, the terminal of the cathode is marked positive (+).

Mn+ (oxidized agent) + n e− → M (reduced agent)

Although oxidation-reduction reactions, also known as Redox reaction, occur simultaneously in galvanic cell to produce electricity. It's more convenient to think about the oxidation and reduction processes separately. The two half-reactions are represented by two half-equations, one for the oxidation reaction and another is the reduction reaction. The quantity of electrons transferred in each direction should be an equivalent, therefore the two half-cells are combined to grant the whole-cell electrochemical reaction.

Example of Oxidation- Reduction (Redox) reaction:

The reaction between zinc and hydrochloric acid

Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)

The zinc losses electrons and is oxidized to form zinc ions

Oxidation: Zn(s) → Zn2+(aq) + 2e-

And the hydrogen ions from the hydr...

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