To Determine the Presence of Anodes and Cathodes in Corrosive Process

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1. The deep blue colour is seen around the nail in a short period of time. This shows the presence of ferrous ions only in this case. Iron that makes up the nail reacts with water. Iron which is more reactive than the hydroxyl molecule as shown in the EMF series acts as anode. Along with this, iron acts as anode and it gives up two electrons to form cation, Fe2+. As a result, the presence of ferrous ions in the solution is detected by the potassium ferricyanide indicator that produces deep blue colour. 2. (i) For the nail with partially zinc plated strip was placed, zinc acts as the anode in which it releases the electrons to become cation. Iron, on the other hand, is the cathode where it accepts the electrons to become anion. It is because zinc is more reactive than iron. (ii) The deep blue colour is only seen around the part of the nail in which zinc is not plated. This also shows the presence of ferrous ions in the solution only. Zinc provides sacrificial protection to iron. Before the iron rusts, zinc is more ready to corrode first. Thus, in this experiment, only the part of the nail that is not plated with zinc rusts (the formation of Fe2+ ) as there is no protection provided on it to prevent corrosion. 3. (i) For the nail with partially tin plated strip was placed, iron acts as the anode in which it releases the electrons to become cation. Tin, on the other hand, is the cathode where it accepts the electrons to become anion. It is because iron is more reactive than tin. (ii) The pink colour is only seen around the part of the nail in which tin is not plated. This indicates the presence of hydroxyl ions in the solution. The rusting takes place in this

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