As a result oxidation reaction takes place at the cathode and cathode material regains its previous state (when it was not discharged). Due to this reduction reaction, the anode material will regain electrons and returns to its previous state when the battery was not discharged.Īs the positive terminal of the DC source is connected to the cathode, the electrons of this electrode will be attracted by this positive terminal of DC source. Actually in the case of discharge of battery, reduction reaction takes place at cathode. Reduction reaction takes place in the anode instead of cathode. Now, due to external DC source, electrons will be injected in the anode. The negative terminal of the DC source is connected to the negative plate or anode of the battery and positive terminal of the source is connected to the positive plate or cathode of the battery. In cathode, reduction reaction takes place and due to this reduction reaction, nickel oxyhydroxide becomes nickel hydroxide by accepting electrons.ĭuring charging of battery, external DC source is applied to the battery. The cathode of this battery is made of nickel oxyhydroxide or simply nickel oxide. During oxidation at anode cadmium metal reacts with OH – ion and releases two electrons and becomes cadmium hydroxide. Here, cadmium is the anode or negative electrode. Let us take a practical example for illustrating discharge of battery. Now the products of oxidation reaction at anode are positive ions or cations, that will flow to the cathode through the electrolyte and at the same time, products of reduction reaction at cathode are negative ions or anions, that will flow to anode through the electrolyte. In cathode these electrons are accepted, that means cathode material gets involved in reduction reaction. The electrons which are excess in anode, now flow to the cathode through external load. On the other hand during discharging of battery, the other electrode involves in reduction reaction. This electrode is referred as negative electrode or anode. The electrode, where oxidation takes place, the number of electrons becomes excess. When an external load is connected to these two electrodes, oxidation reaction starts occurring in one electrode and at the same time reduction occurs in other electrode. In a battery there are two electrodes immersed in an electrolyte. As the oxidation number is decreased or reduced, this part of the reaction is called reduction. On the other hand, when an atom accepts electrons, it’s negative oxidation number increases, which means oxidation number of the atom decreases in respect of zero reference. As the oxidation number increases, this part of the reaction is referred as oxidation reaction. Here in our example the oxidation number of zinc becomes + 2 from 0. In this reaction as the zinc gives up electrons, it is oxidised and the chlorine accepts electrons, hence it is reduced.Īs when an atom gives up electron, its oxidation number increases. Now, these two oppositely charged ions combine together to form, zinc chloride (ZnCl 2) Here, each chlorine atom accepts one electrons and becomes negative ion. In the above reaction zinc (Zn) first gives up two electrons and becomes positive ions. Let us consider the reaction between zinc metal and chlorine. Because, battery are discharged or charged due to oxidation and reduction reactions.įor understanding the theory of oxidation and reduction, we can directly go to an example of chemical reaction. charging and discharging of battery, we will first try to understand what is oxidation and reduction. Before going in detail of this subject i.e.
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