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Class 9
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Chemistry
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Electrochemistry
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Batteries (Dry Cell & Lead Storage Battery)

Electrochemistry

Batteries (Dry Cell & Lead Storage Battery)

Chemistry

BATTERIES:

A battery consists of group of galvanic cells connected in a series.

We use lot of electrical devices having batteries as a source of electricity

Examples of batteries include dry cell, lead storage battery, mercury battery etc.

Batteries are classified as primary (non-rechargeable form) and secondary (rechargeable form)

DRY CELL (Primary Cell):

It is also known as Leclanche cell. It is a type of primary cell which produce electricity using redox reaction between their chemical substances placed in it.

It uses zinc as anode, manganese dioxide as cathode and aqueous ammonium chloride (NH4_44​Cl) or zinc chloride (ZnCl2_22​) as electrolyte. A copper cap is fixed on the top of the carbon rod for conduction of electricity. Zinc and graphite are then connected by a metal wires as a result following chemical reactions take place;

At Anode: Zn0^00 ⟶\longrightarrow⟶ Zn+2^{+2}+2 + 2e−^-−

(Oxidation)

At Cathode:

2NH4_44​+^++ + 2MnO2_22​ + 2e−^-− ⟶\longrightarrow⟶ Mn2_22​O3_33​ + 2 NH3_33​ + H2_22​O

(Reduction)

It produces a potential of 1.5 volts.

SECONDARY STORAGE BATTERY (LEAD STORAGE BATTERY):

A battery is a device which produces electricity through electro chemical reactions. Lead storage battery is an example of secondary cell in which chemical changes can be reversed. It has several voltaic cells connected in series .It contain lead plates which serve as anode and lead oxide (PbO) which acts as cathode. These electrodes are immersed in electrolytic solution of dilute sulphuric acid (H2_22​SO4_44​). Chemical changes during charging and discharging processes can be shown as;