A simple device used for estimating the concentration of total dissolved solids in an

Chapter 13, Problem 13.140

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A simple device used for estimating the concentration of total dissolved solids in an aqueous solution works by measuring the electrical conductivity of the solution. The method assumes that equal concentrations of different solids give approximately the same conductivity, and that the conductivity is proportional to concentration. The table below gives some actual electrical conductivities (in arbitrary units) for solutions of selected solids at the indicated concentrations (in ppm by mass): Conductivity Sample 0 ppm 5.003103 ppm 10.003103 ppm CaCl2 0.0 8.0 16.0 K2CO3 0.0 7.0 14.0 Na2SO4 0.0 6.0 11.0 Seawater (dil) 0.0 8.0 15.0 Sucrose (C12H22O11) 0.0 0.0 0.0 Urea [(NH2)2CO] 0.0 0.0 0.0 (a) How reliable are these measurements for estimating concentrations of dissolved solids? (b) For what types of substances might this method have a large error? Why? (c) Based on this method, an aqueous CaCl2 solution has a conductivity of 14.0 units. Calculate its mole fraction and molality.