The Total solution for NCERT class 6-12
A sample of drinking water was found to beseverely contaminated with chloroform, CHCl3, supposed to becarcinogenic in nature. The level of contamination was 15 ppm (by mass).
(i) Express this in percent by mass.
(ii) Determine the molality of chloroform in the watersample.
(i) 1 ppm is equivalent to 1 part out of 1 million (106)parts.
Mass percent of 15 ppm chloroform in water
(ii) 100 g of the sample contains 1.5 × 10–3 gof CHCl3.
⇒ 1000 g of the sample contains 1.5 × 10–2 gof CHCl3.
Molality ofchloroform in water
Molar mass of CHCl3 = 12.00+ 1.00 + 3(35.5)
= 119.5 g mol–1
Molality ofchloroform in water = 0.0125 × 10–2 m
= 1.25 × 10–4 m