2 Electrolysis and Electrical Conductance - Electrolytes and Non-electrolytes- Electrolysis and it’s mechanismElectrical UnitsCoulombAmpereOhmVolt
3 Faraday’s Law of Electrolysis First Law:The amount of a given product liberated at an electrodeduring electrolysis is directly proportional to the quantityof electricity which passes through the electrolyte solution.Second Law:When the same quantity of electricity passes throughsolutions of different electrolytes, the amounts of thesubstances liberated at the electrodes are directlyproportional to their chemical equivalents.
4 The electrical Unit Faraday The quantity of electricity required to liberate one gram-equivalentof a substance is 96,500 coulombs. This quantity of electricity is knownas Faraday (F).1 Faraday = 96, 500 coulombs = 1 Mole electrons
5 Conductance or Conductivity The power of electrolytes to conduct electric currents is termed asconductivity or conductance.I = E / R, where I= current flow,E=potential differences at two ends, R=resistanceSpecific resistance:R α l / A R = ρ x l/A
6 Specific conductance: The conductance of one centimeter cube (cc) of a solutionof an electrolyte.Κ = 1 / ρEquivalent conductanceThe conductance of an electrolyte obtained by dissolvingone gram-equivalent of it V cc of water.Λ = κ x V
7 Molar conductanceThe conduction of all ions produced by one mole(one gram-molecular weight) of an electrolyte whendissolved in a certain volume V cc.μ = κ x V
9 Kohlrausch’s LawThe equivalent conductance of an electrolyte at infinitedilution is equal to the sum of the equivalent conductancesof the component ions.λ∞ = λa + λc
10 Ostwald’s Dilution Law Limitation:Holds good only for weak electrolytes and fails completely whenapplied to strong electrolytes.
11 Electrochemical Reactions In electrochemical reactions, electrons are transferred from one species to another.Electrochemical CellsA device for producing an electrical current from achemical reaction (redox Reaction) is called anelectrochemical cell.How a Redox reaction can produce an electrical current?
12 Electromotive Force (emf) Water only spontaneously flows one way in a waterfall.Likewise, electrons only spontaneously flow one way in a redox reaction—from higher to lower potential energy.
13 The potential difference between the anode and cathode in a cell is called the electromotive force (emf).It is also called the cell potential, and is designated Ecell.Ecell= Ered (cathode) − Ered (anode)
14 Single electrode potential: The potential of a single electrode in a half-cellis called the single electrode potential.Standard EMF of a cell (Eᴼ)The emf of a cell with 1 M solutions of reactants and productsIn solution measured at 25 ᴼC.
15 Voltaic CellsA voltaic cell is one in which electrical current is generatedBy a spontaneous redox reaction.Predicting the oxidizing or reducing abilityPredicting whether a metal will displace another metalfrom it salt or not
17 Multiple Choice Questions Question 1. The conductivity of an electrolyte is due to thePresence of ions in the electrolytefree movement of ions in the solutionreunion of ions in the solutionrelease of heat energy due to ionisationKey : (b)
18 Question2. The electrical conductivity of an electrolyte depends upon The number of molecules in the electrolytethe number of ions present in the electrolytethe number ions present in the solutionthe number of molecules of the solventKey: (c)
19 Question 3. Ostwald’s dilution law is applicable to All electrolytes strong electrolytesweak electrolytesnon-electrolytesKey (C)
20 Question 4. The site of oxidation in an electrochemical cell is The anodethe cathodethe electrodethe salt bridgeKey : (a)
21 Question 5. The salt bridge in the electrochemical cell serves to Increase the rate at which equilibrium is attainedincrease the voltage of the cellmaintain electrical neutralityincrease the oxidation/reduction rateKey : (C)