InterviewSolution
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InterviewSolution
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(a) Define molar conductivity of a solution and explain how molar conductivity changes with change in concentration of solution for a weak and a strong electrolyte. (b) The resistance of a conductivity cell containing 0.001 M KCl solution at 298 K is 1500 Omega.What is the cell constant if the conductivity of 0.001 M KCl solution at 298 K is 0.146 xx 10^(-3) S cm^(-1)? |
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Answer» Solution :(a) MOLAR conductivity is the conductivity of all the ions produced by ionisation of 1 G mol of an electrolyte when present in V mL of solution. It is denoted by `Lambda_(m)`. where V = volume in mL containing 1 g mol of the electrolyte `Lambda_(m) = k xx 1000/C` where C = concentration of the solution in g mol/L. Variation of molar conductivity with concentration for strong electrolytes - Molar conductivity increases slowly with dilution. It approaches a limiting value when the concentration approaches zero. This value is called molar conductivity at infinite dilution `Lambda_(m)^(@)`. Variation of conductivity with concentration may be given by: `Lambda_(m)= Lambda_(m)^(@) =AC^(1//2)`, where A is a constant and C is concentration. Variation of molar conductivity with concentration for weak electrolytes - Variation of `Lambda_(m)`with concentration is very large to the EXTENT that we cannot obtain molar conductance at infinite dilution `Lambda_(m)^(@)`by extrapolation of `Lambda_(m)` VS `C^(1//2)` plots. (b) Conductivity `K = 0.146 xx 10^(-3) S cm^(-1)` Resistance = R= 1500 ohm Cell constant = Conductivity (k) `xx` Resistance (R) `=0.146 xx 10^(-3) S cm^(-1) xx 1500 Omega` `=0.219 cm^(-1)` |
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