What is Electrolysis?
Electrolysis is a process where chemical changes occur at the electrodes (cathode or anode) due to the passage of electricity passes through the electrolytic solution. In chemistry, the process of electrolysis is carried out by oxidation reduction or redox reaction by which the substance losses or gains electrons. Electrolysis technology is a commercially important process for the extraction or purification of metals (copper, nickel, silver, gold) from their naturally occurring ores or minerals by using electrolytic cell reaction.
Process of Electrolysis
The process of electrolysis and the mechanism of electric conductance of hydrochloric acid solution define that there is a surplus of electrons at the cathode and a deficit of electrons at the anode.
The hydrogen ion (H+) in solution moves toward cathode by Coulombic force of attraction and receives one electron to form the hydrogen atom. In a similar way, chlorine ion from the solution moves towards the anode, departs one electron to form a neutral chlorine atom. Therefore, one-electron transfers from the cathode to the anode with the help of hydrochloric acid solutions or medium, and due to the conductance of electric current or electrolysis, the ions are decomposed at the electrode. Two hydrogen atoms form hydrogen gas and two chlorine atoms form chlorine molecule, escape from the electrolytic solution.
Faraday’s first law of electrolysis states that the amount of decomposition at the electrode (w) is directly proportional to the quantity of electric current or electricity (Q) passed. The mathematical formula of the first law, w = ZQ, where w = electrochemical equivalence of decomposing substances. Again, w = ZIt, where, I = current strength or amount of electricity passing in unit time, t = time of flow of electricity. Therefore, one faraday defines the amount of electricity required to decompose one gram equivalent electrolysis substance in chemistry or chemical science, and the numerical value of 1F = 96496 coulombs ≈ 96500 coulombs. Therefore, the electrochemical equivalence of silver (atomic mass = 108), ZAg = 108/96500 = 0.001118 gm/coulomb. This law used to construct the instrument Coulometer to determine the amount of electricity passing through the circuit by determining the quantity of substance decomposes at an electrode in electrolysis solution.
Faraday’s second law of electrolysis states that the weight of different substances decomposed at the different electrodes by given electricity is proportional to their equivalent weight. The mathematical formula of the second law of electrolysis, w1/w2 = E1/E2, where w1 and w2 = weight of a decomposed substance and E1 and E2 = equivalent weights. In learning chemistry, this law helps to determine the Avogadro number (N0). For the decomposition of 1-mole substance at the electrode, ZF electricity required, and 1-mole substance ZeN0 amount of charge. Therefore, ZeN0 = ZF or N0 = F/e. The numerical value of Avogadro number = 96500/1.6 × 10-19 = 6.023 × 1023.
Uses of Electrolysis
The electrolysis process has many important industrial applications, for extraction (electrowinning) or purification (electrorefining) of metals and non-metals (aluminum, lithium, sodium, magnesium, copper, silver, gold, fluorine, chlorine) from ores or compounds, for coating or electroplating of metals. The molten sodium chloride produced metallic sodium and chlorine molecule but the electrolysis of the aqueous solution of sodium chloride produced sodium hydroxide and chlorine gas. The process of electrolysis is used for the production of hydrogen and oxygen from water solution. Electrolysis formula used fuel cells, which work by producing chemical energy by combustion of fuels like hydrogen, carbon monoxide, methane, propane, methyl alcohol is directly converted into electrical energy used for a pollution-free continuous source of energy in spacecraft and nuclear submarines.