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State and explain Kohlrausch's law ofindependent migration of ions. |
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Answer» Solution :Statement of Kohlrausch's LAW: This statesthat of INFINITE dilutionof the solution,each ionof an electrolytemigratesindependentlyof its co-ionsand contributesindependentlyto thetotalmolarconductivityof the electrolyte, irrespectiveof the natureof otherions presentin te solution . Explanation :Both theions, cationand anionof the electrolytemake a definitecontributionto the molar conductivity ofthe electrolyte at infinite dilution or ZERO concentration`(wedge_(0))`. Of `lambda_(+)^(0)` and `lambda_(-)^(0)`are the molarconductivities of cation and nation respectively at infinite dilution, then `wedge_(0) = lambda_(+)^(0) + lambda_(-)^(0)` . This is known as Kohlrausch's law of independentmigrationof ions. `wedge_(0KCl) = lambda_(K^(+))^(0) + lambda_(Cl^(-))^(0)` and `wedge_(0NaCl) = lambda_(Na^(+))^(0) + lambda_(Cl^(-))^(0)` `:. wedge_(0KCl) - wedge_(0NaCl)` `= (lambda_(K^(+))^(0) + lambda_(Cl^(-))^(0)) - (lambda_(Na^(+))^(0) + lambda_(Cl^(-))^(0)) = lambda_(K^(+))^(0) - lambda_(Na^(+))^(0) + lambda_(I^(-))^(0)` `:. wedge_(0KI) - wedge_(0NAl) = (lambda_(K^(+))^(0) + lambda_(I^(-))^(0)) - (lambda_(Na^(+))^(0) + lambda_(I^(-))^(0))` `= lambda_(K^(+))^(0) - lambda_(Na^(+))^(0) = 150.3- 126.9 = 23.4` Thus the difference in `wedge_(0)` valuesfor `K^(+)` and `Na^(+)` saltsis constant and is independentof the nature of other ANIONS. This provesthe validity of Kohlrausch's law. |
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