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| Simple Voltaic Cell |
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| In order to study the working of an electrolytic cell and the phenomena of electrolysis it is important to know the working of a galvanic or a voltaic cell that generates electrical energy from its chemical reaction. |
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| In a simple voltaic cell a zinc plate and a copper plate are immersed in a very dilute solution of sulphuric acid, taken in a glass vessel. These two metal plates are called electrodes and the solution is called the electrolyte. The copper plate and the zinc plate are externally connected to a bulb as shown in the figure 4.7. |
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| Zinc loses electrons more readily than copper, as it is more electropositive than copper. Each zinc atom loses two free electrons and hence gains two units of positive charge. |
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| As copper is lower in the metal activity series, it does not undergo a similar reaction and hence remains a region of deficiency of electrons. So, when the zinc plate and the copper plate are connected by means of a metal wire, free electrons from the zinc plate flow to the copper plate and the bulb connected externally starts glowing. |
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| Some of these electrons get added to hydrogen ions of the sulphuric acid of the electrolyte, to form free hydrogen. |
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| It may be noted that in a voltaic cell, that the direction the flow of electrons is not affected if the position of the two metals is reversed. |
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| As zinc metal is oxidised to zinc ions, oxidation occurs here. The electrons given up by zinc leave the cell from this electrode and travel the external circuit to copper electrode. Here, the electrons enter the cell and bring about the reduction of the hydrogen ions of the sulphuric acid. Thus an electric current is delivered as a result of a spontaneous oxidationreduction reaction. |
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