Question

Account for the following observation :-
1. In a dry cell the build up of ammonia gas around the carbon cathode should disrupt in electric current but in practice this does not.

Answer 1

Answer:

dry cell is a compact form of LeClanche cell. It consists of an outer container made of inc, which acts as anode. The zinc container is lined from inside with a porous insulating paper.

The cathode is a carbon rod having a brass cap. The zinc container lined from inside with a porous insulating paper. The space between the cathode and anode is filled with a mixture of MnO2 and a thick paste of ammonium chloride, (NH4Cl), zinc chloride (ZnCl2), and charcoal. The porous paper lining prevents a direct contact between zinc container and the paste, and acts as a salt bridge.

Answer 2

In Dry cell the build up of ammonia gas around the carbon cathode should disrupt in electric current but in practice this does not because of following reasons :

• Dry cell consists of two electrodes, one is anode and another is cathode. The anode is made up of zinc casing. The cathode consists of a carbon rod with casing of manganese dioxide and ammonium chloride.

• When we continuously use dry cells, they steadily lose their current due to formation of ammonia gas. This ammonia gas surrounds the carbon cathode and insulates it which leads to decrease in current.

• If dry cell is allowed for some rest then the ammonia gas formed get diffused toward anode and forms complex ion Zn(NH₃)₄²⁺ when combine with zinc ions. When this complex ion forms, the cell begins to deliver strong current again.

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