Explain the Chemical Reaction in a Lead Acid Battery.

In this article, I will discuss the chemical reaction in a lead-acid battery. 

Chemical reaction in a lead acid battery

Chemical Reaction in a Lead Acid Battery

The chemical reaction in a lead acid battery takes place in three chemicals in the battery. In the presence of sulphuric acid, the electrons form one group of plates. This transfer of electrons is continued until there is a sufficient imbalance of electrons to create a 2 volts pressure between the two groups of plates. This results in a pressure of 2 volts between the terminals of the battery cell.
If the two terminals are connected by a circuit the electrons will flow. They flow from the terminal where the chemical reaction has collected them through the circuit from the other terminal where the chemical reaction has taken them away. The chemical reactions use up the sponge lead, lead peroxide, and sulphuric acid. Thus, after a certain amount of current has been withdrawn, the battery is discharged or dead, or run down. When it is discharged, it is not capable of delivering any additional current. It may then be recharged. 

What are the Chemicals Used in Batteries

The chemicals used in a battery are as follows- 
  1. Sponge Lead(Solid).
  2. Lead Oxide(paste).
  3. Sulphuric Acid(Liquid).
The sponge lead and lead peroxide are held in plate grids to form negative and positive plates. Sulphuric acid mixed with water is filled in the container and the plates along with the separators are held in it. The three substances thus react chemically to produce a flow of current. This plate grid consists of a framework of antimony alloy with interlocking horizontal and vertical bars, which serve to hold the paste in the plate.

Chemical Reaction in the Lead-Acid Battery

When the battery is discharging the sulphuric acid is broken up into two parts- hydrogen and sulphate. The hydrogen is liberated at the lead oxide, which combines with parts of sulphuric acid to form lead Sulphate and water. The Sulphate is liberated at the spongy lead plates and combines with them to form lead Sulphate. 
During this process, the electrolyte becomes dilute because of the absorption of SO4 by the sponge lead plates.


Chemical equation in a lead acid battery.
When the battery is charged, the chemical reaction described above is reversed. The lead sulfate on the plates is again converted to lead peroxide, and the lead Sulphate on the other plate is reduced to spongy lead. The electrolyte becomes concentrated because of the increased amount of Sulphuric Acid.

Ending Up With

The battery cell is a means of converting electrical energy into chemical energy during charging and chemical energy into electrical energy during discharging. 
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