The simple voltaic cell is the most primitive form of a battery cell. The Italian physicist Allesandro Volta discovered that when a copper and zinc metal separated by dilute sulfuric acid, form a battery cell.
Construction of his cell was quite simple. He placed copper sheets and zinc sheets alternatively in a column. Then we inserted blotting paper wed with dilute sulfuric acid in between each of the copper and zinc sheets. And in this way, he formed his first cell.
After his name, this cell became famous as the voltaic cell. Although we can construct a simple voltaic cell simply by immersing one copper rod and one zinc rod into dilute sulfuric acid.
Construction of Simple Voltaic Cell
For constructing a simple voltaic cell we first take a jar. Then we fill it with dilute sulfuric acid. After that, we partly immersed one copper and one zinc rod into that dilute acid.
Electrolyte of Voltaic Cell
The dilute sulfuric acid is the electrolyte of this cell.
Here the copper rod behaves as a positive electrode as the simple voltaic cell. Also, we call this positive electrode as anode.
On the other hand, the zinc rod behaves as a negative electrode or cathode.
Chemical Reaction in Voltaic Cell
As soon as we connect one electrode load across the copper and zinc rod, a current starts flowing from anode to cathode through the load. In other words, the current will flow from copper rod to zinc rod through the external load.
Before discussing the details of the chemical reactions taking place inside the simple voltaic cell we need to see the electro negativity values of copper and zinc. The electro negativity of copper is 1.9. The same for zinc is 1.65. As the electro negativity of copper is more than that of the zinc, the copper undergoes in the reduction reactions. Whereas for less electro negativity compared to copper, the zinc with go through an oxidation reaction.
In dilute sulfuric acid, the H+ ions and SO4– – ions exist separately in the aqua solution. Since, the zinc is less electro negative than copper, zinc atoms release and become positive zinc ion (Zn++)
Again due to more electro negativity than that of zinc the copper will undergo in reduction reactions. For that the electrons, the zinc rod will travel to the copper rod through the load. Now the sulfate ions (SO4– –) will react with positive zinc ions (Zn++) will combine with zinc and form zinc sulfate. Then this zinc sulfate dissolves in the aqua solution as Zn++ and SO4– – ions. As a result, the weight of the zinc reduces and it gets dissolved in the aqua electrolyte.
On the other side, the copper rod will supply the extra electrons accumulated inside the anode to H+ ions. Therefore the hydrogen ions become hydrogen atoms and form one hydrogen molecule (H2). Consequently, there will be bubbles of hydrogen gas (H2) coming out along anode (copper rod).
EMF of Simple Voltaic Cell
The reduction potential of zinc is -0.76V and the reduction potential of copper is +0.34V. Therefore emf of a voltaic cell is 0.34+0.76=1.1V.
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