A sample of drinking water was found to be severely contaminated with chloroform (CHCl _(3)) supposed to be a carcinogen. The level of contamination was 15 ppm (by mass) (i) express this in percentage by mass (ii) determine the molality of chloroform in the water sample.

A sample of drinking water was found to be severely contaminated with

1.	A sample of drinking water was found to be severely contaminated with chloroform (CHCl _(3)) supposed to be a carcinogen. The level of contamination was 15 ppm (by mass) (i) express this in percentage by mass (ii) determine the molality of chloroform in the water sample.
Answer» Solution :(i) 15 ppm means 15 parts in MILLION `(10^(6))` parts by mass in the solution `therefore %` of mass `= (15)/(10^(6) xx 100 = 1.5 xx 10 ^(-4)` (ii) Taking 15 g chloroform in `10^(6)` g of the solution Mass of the solvent `= 10 ^(6)g` Molar mass of `CHCl_(3) = 12 + 1 + (3 xx 35.5) = 119.5 g mol^(-1)` `therefore`Molality `= ((15)/(119.5))/(10^(6)) xx 100 = 1.25 xx 10 ^(-5)m`