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Give a note on effect on conductivity of solution when change in concentration of solution. |
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Answer» Solution :* Both conductivity and molar conductivity change with the CONCENTRATION of the electrolyte. * Conductivity always decreases with decrease in the concentration, both for weak and strong electrolytes. * This can be explained by the fact that the number of IONS per UNIT volume that carry the current in a solution decreases on dilution. * The conductivity of a solution at any given concentration is the conductance of one-unit volume of solution kept between two platinum electrodes with unit area of cross section and at unit length. * conducitivyt of solution : Molar conductivity of a solution at a given concentration is the conductance of the volume V of solution containing one mole of electrolyte kept between two electrodes with area of cross section A and distance of unit length. * If conductivity area of conductivity=A, Distance between two Pt electrode=l, then `G=kappa((A)/(l))` But if A=1 and l=1, then `therefore G=kappa((1)/(1))` So G=`kappa`=conductivity of solution * Molar conductivity and volume of solution : At given concentration, two Pt electrode which have cross sectional area A and having unit length of volume, then the volume of solution between two Pt electrode which has 1 mol electrolyte, has conductivity `(Lamda_(m))`. `(Lamda_(m)=(kA)/(l))` If A=1 and l=1 then, `Lamda_(m)=kappa` If solution has l=1, A=V=1 mol electrolyte, then `Lamda_(m)kappaV` Molar conductivity of a solution at a given concentration is the conductance of the volume V of solution containing one mole of electrolyte kept between two electrodes with the area of cross section A and distance of unit length. * Effect on molar conductivity when change in concentration of solution: If the concentration of solution decreases, then volume of solution has 1 mol of electrolyte INCREASES and so molar conductivity increases. So, volume increases then concentration decreases. So molar conductivity `Lamda_(m) prop(1)/("Concentration of solution")` * Decrese in concentration of solution means dilution of solution and decrease in conductivity of SOLUTIO is more than that of the volume. * `Lamda_(m)` can be defined as the conductance of the electrolytic solution kept between the electrodes of a conductivity cell at unit distance but having area of cross section large enough to accommodate sufficient volume of solution that contains one mole of the electrolyte. * Limit molar conductivit : When molar conductivity of solution is about zero, then molar conductivity is known as limiting molar conductivity which is denoted by `Lamda_(m)^(@)`. The variation in `Lamda_(m)` with concentration is different for strong and weak electrolytes. |
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