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Chapter – 14 Chemical Effects of Electric Current Materials through which electric current can pass through easily are called conductors of electricity. Electrical conductivity is a measure of the ability of a substance to allow theflow of an electric current. Among solids metals and graphite aregood conductors ofelectricity which have highelectrical conductivity. Someliquids are alsogood conductors. Pure water or distilled wateris a poor conductor of electricity. But the presence of even small amount of impurities(salts and minerals) makes water a good conductor as it contains ionsthrough which conduction takes place. Hence water from taps,wells, ponds, rivers, seas, lakes, etc. conduct electricity as theycontain impurities. Most liquids that conduct electricity are solutions of acids, basesand salts. Whenelectricity is passed through a conducting solution, the molecules of the solution dissociate into ions. Ions are atoms or group of atoms with a positive or a negative charge. These ions cause electrical conduction through the liquid. A liquid Thatconducts electricity dueto the presence of ions is called anelectrolyte. Electrolysis: The process of decomposition of a chemical compound in a solution whenan electric current passes through itis called electrolysis. This process isdue to thechemical effect ofelectric current. Two electrodes are inserted in the solution and are connected to the terminals of a battery with a switch in between. This arrangement is called an electrolytic cell. The electrode that is connected to the positive terminal of thebattery is called the anode, andthe other connected to the negative terminal is called the cathode. Electrolysis isused in refining and extraction of metals fromimpure samples. Thisprocess is called electrorefining. It isalso useful incoating one metal with another. Thisprocess is called electroplating.
The passage of an electric current through a conducting solution causes chemical reactions. This is knownas the chemical effect of electric current. Some ofthe chemical effects of electric current arethe following: Formation of bubbles of a gason the electrodes Deposition of metalon electrodes Change in colour of solutions Electroplating:The process ofdepositing a layer of any desired metal on another material by means of electricity iscalled electroplating. The object to be electroplated is made thecathode (negative electrode) by connecting itto the negative terminal of the battery. The metal which has to be deposited is made the anode (positive electrode) by connecting it to thepositive terminal of the battery. The electrolyte is usually a saltsolution of themetal to becoated. Application ofElectroplating: (i) Metals thatrust are often coated with other metals to prevent rusting. (ii) Chromium plating is found on bath taps,car bumpers, etc.to give a bright attractive appearance and resist scratches and wear. (iii) Silver plating is done oncutlery and jewellery items. (iv) Tin cans, used for storing food, are made by electroplating tin onto iron. Tin is less reactive thaniron. Thus, fooddoes not comeinto contact withiron and isprotected from getting spoilt.
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