Question

Carbon rod in a dry cell acts as anode, which is insulated from cathode by:
A. The use of polarisation
B. Local action
C. Means of a tar paper washer
D. Both A and B

Answer 1

Hint:The anode and cathode of cells are to be are separated using certain ion-exchange membranes in order to retain the purity of hydrogen gas and also to prevent the anodic bacteria to consume the hydrogen that is produced electrochemically. Our answer should be a material that is capable of permitting the proper working of the cell by insulating the electrode.

Complete answer:
Usually in dry cells, Ammonium Chloride ($NH4Cl$) is used as the electrolyte. The anode and cathode mustn’t combine with the electrolyte as it causes unwanted reactions during the process. Hence, we need an insulator to protect the electrode and to facilitate the reactions. Tar paper washer is a great insulator and it is capable of protecting anode from combining with cathode or electrolyte.

Hence, the correct option is option C.

Note:Dry cell is also termed as Leclanche’s cell and it is considerably dry as the electrolyte is in the form of a paste. This avoids spillage and makes it easily portable. Sometimes fibrous fabrics can also be used to separate the electrodes in a dry cell. Along with insulation properties, tar paper is also a waterproof material and is commonly used for roofing purposes in many areas.