dear all,
i have a doubt regarding Faraday's law in electrolysis
According to faraday's law, how does the concentration (of an electrolyte) affect the amount of the substance deposited at an electrode during an electrochemical reaction
please help me
tanks in advance
It does not affect (in principle). It is determined by the amount of electricity (coulombs) that have been put into the system.
concentration does not have much effect. The amount of substance deposited depends on the amount of charge that is passed. Only the diffusion properties of the analyte will change depending upon the viscosity of the electrolyte. It may affect the amount of substance that is deposited.
The equation applies only if the current efficiency (CE) of the metal deposition reaction is 100 %. In the equation, Epsilon and F are constants and do not vary with concentration. As you prolong time of electrolysis, concentration of metal ion in the solution goes down (assuming the anode reaction is not dissolution of the same metal. If we maintain I constant (say using a galvanostat), electrode potential keeps increasing making it possible for parasitic reactions to occur, lowering the CE for metal deposition reaction. (You may note, that your question implies a single value of concentration for the solution. Therefore, your experiment must satisfy that condition!)
The above is explanatory in nature.
The alternative and brief answer would be: Write the RHS of the equation as applicable to the reaction of interest. You may write RHS using subscript m, for I and epsilon. Written thus, the equation expresses Faraday's law correctly.
Faraday's laws are, by implication, statements of laws of conservation mass and of electric charge. As long as these laws are valid, Faraday's laws would be valid!
P. Radhakrishnamurty
I would like to know if there is any device to measure the concentration of the metal ion in the solution/electrolyte as metal ion concentration goes down when the electro deposition continued for long time (where the anode reaction is not dissolution of the same metal).@ Radhakrishnamurty Padyala
I am not an expert in analytical chemistry. Polarography or some such instrumental methods may be available besides chemical methods to measure concentration of metal ion in solution.
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