Redox reactions and Electrochemistry - TestBag

Redox reactions and Electrochemistrydirectly proportional to their equivalent masses or electrochemical equivalents. For example, if same quantityof electricity produces the product A and B at the respective electrodes of the electrolytic cells connected inseries, thenMass of AMass of B=Equivalent mass of AEquivalent mass of B=ECE of A.ECE of BApplications of electrolysis : (i) Determination of equivalent masses of elements, (ii)Electrometallyurgy, (iii) Manufacture of non -metals, (iv) Electroplating of metal, (v) Manufacture ofcompounds, (vi) Electroplating – The process of coating an inferior metal with a superior metal by electrolysis.11.12 Conductivity.Conductivity is a measure of the ease with which current flows through the conductor. It is the reciprocal−1−1of resistance. Its units are Ω or ohmC 1 1 a= = .R P× lor mho or S (Siemens)Note : Resistance of metallic conductor decreases with rise in temperature while resistance ofelectrolyte increases with rise in temperature.Specific conductivity () is reciprocal of specific resistivity.(1) It is the conductance of one centimeter cube of the conductor.(2) It is denoted by Greek letter Kappa ().−1 −1−1−1−1(3) Units are ohm cm or Ω cm or S cm .2(4) For a conductor of length/cm and area of cross-section a cm .1K =P1 ⎛= ⎜R ⎝la⎞⎟ or⎠⎛ l ⎞C ⎜ ⎟ .⎝ a ⎠(5) In case of electrolytic cells, where a is the area of cross section of electrodes and l is the distancebetween the electrodes, the quantity al−1is called cell constant. Its unit is cm .(6) The conductivity of electrolytic solution decreases with the increase in dilution because dilution3decreases in the number of ions per cmof the solution.Equivalent conductivity ( ) : It is conductance of a solution containing one gram equivalent ofelectrolyte such that, the entire solution is placed between two large electrodes at one centimeter apart.(1) The equivalent conductivity is related to conductivity (k ) of solution as,number of gm-equivalents of electrolyte per litre of solution i.e., normality of solution.k × 1000Λ =N2 1(2) The equivalent conductivity is expressed in the units of ohm −1 cm equi−2 −1or S cm euqi .Where, N is theMolar conductivity () : It is defined as the conductance of the solution containing one gram-mole ofthe electrolyte such that the entire solution is placed between two electrodes one centimeter apart.(1) Molar conductivity is related to conductivity (k) by the relationk × 1000 = , where, M is the molarity of solution.M(2) Units of are ohm−1 −1cm−1 −1mol or Ω2cm−12mol or S − cm−1mol .