Question 1.TE.17: A sample of drinking water was found to be severely contamin......

(i) 15 ppm means that 15 parts of chloroform is present in 10^6 parts.

∴ % by mass of CHCl_3 = \frac{15}{10^6} \times 100 = 1.5 \times 10^{-3} \%

(ii) Molar mass of CHCl_3 = 12 + 1 + 3 × 35.5 = 119.5

Moles of CHCl_3 = \frac{1.5\ \times\ 10^{-3}\ \text{g}}{119.5\ \text{g mol}^{-1}}

= 1.255 \times 10^{-5}

Mass of water = 100 g

∴              Molality = \frac{1.225\ \times\ 10^{-5}}{100} \times 1000

= 1.255 \times \pmb{10^{-4}} m