Commercial Cells

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Commercial Cells
Galvanic Cell
A Galvanic cell is also known as a Voltaic cell. It was named after Luigi Galvani and Alessandro Volta. A galvanic cell is capable of producing an electric current from a redox reaction that occurs within it and consists of two half cells. Each half cell consists of an electrode and electrolyte and a salt bridge. In a galvanic cell one metal can undergo reduction and the other oxidation. A typical galvanic cell is based on the spontaneous redox reaction: Net Ionic Equation

Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s)
Half Equations
Zn(s) → Zn2+(aq) + 2e–       
Cu2+(aq) + 2e– → Cu(s)
The anode will undergo reduction (Zinc) and the cathode will undergo oxidation (Copper) The two half cells must be physically separated so that the solutions do not mix together. A salt bridge is used to separate the two solutions yet keep the respective charges in the solution from separating which would cease the chemical reaction. Electrons released during an oxidation half-equation must flow through a wire or other external circuit before they can be accepted in a reduction half-equation. Consequently an electrical current is made to flow. Construction of galvanic cells

Anode
Half-cell where oxidation occurs
Anode
Half-cell where oxidation occurs
The more reactive metal will undergo oxidation which is a loss of electrons. These electrons will flow from the anode (negative terminal) to the cathode (positive terminal) which will then undergo reduction which is the gain in electrons. This flow of electrons creates electricity. The salt bridge allows total charge in each half cell to become neutral.

The more reactive metal will undergo oxidation which is a loss of electrons. These electrons will flow from the anode (negative terminal) to the cathode (positive terminal) which will then undergo reduction which is the gain in electrons. This flow of electrons creates electricity. The salt bridge allows total charge in each half cell to become neutral.

Electrolyte
Electrolyte
Cathode
Half-cell where reduction occurs
Cathode
Half-cell where reduction occurs
Typical Cathode Reaction
Metal Ion + electrons Metal atom
Example
Cu2+(aq) + 2e– → Cu(s)
Typical Cathode Reaction
Metal Ion + electrons Metal atom
Example
Cu2+(aq) + 2e– → Cu(s)
Typical Anode Reaction
Metal atom Metal Ion + electrons
Example
Zn(s) → Zn2+(aq) + 2e–
Typical Anode Reaction
Metal atom Metal Ion + electrons
Example
Zn(s) → Zn2+(aq) + 2e–

Definitions
* Anode – The negative electrode in a galvanic cell, it is found in the half cell where it undergoes oxidation. * Cathode – The positive electrode in a galvanic cell, it is found in the half cell where it undergoes reduction * Electrode – A conducting material placed in each half cell to pick up or release electrons in the redox reaction, e.g. in a galvanic cell there are two electrodes which pick up or release electrons * Electrolyte – A substance which will conduct electricity when molten or in solution, generally, it refers to ionic solutions

Dry Cell
The most common type of battery used today is the dry cell battery. Invented by Sakizou Yai in 1885, the dry cell battery was improved and patented by Dr. Carl Gassner, a German scientist in 1887. A "dry-cell" battery is essentially made of a metal electrode or graphite rod (elemental carbon) surrounded by a moist electrolyte paste enclosed in a metal cylinder.

The dry cell is made of two half cells. The anode is a zinc shell which also acts as the reductant at the negative electrode (anode) and it is where oxidation occurs. The cathode is made of manganese dioxide which is the oxidant, the reduction occurs at this terminal where it gains electrons, the manganese dioxide also surrounds a carbon rod which acts as the positive terminal to increase its conductivity. The electrolyte is an aqueous paste made of ammonium chloride and a mixture of powdered Manganese dioxide, carbon, and...
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