Q. 94.4( 26 Votes )
A sample of drinking water was found to be severely contaminated with chloroform (CHCl3) supposed to be a carcinogen. The level of contamination was 15 ppm (by mass):
(i) express this in percent by mass
(ii) determine the molality of chloroform in the water sample.
Level of contamination = 15 ppm [by mass]
To find: Mass Percentage and Molality
Mass Percentage of Solute
Calculation of Mass Percentage:
15 ppm means 15 parts of Chloroform in 106 parts of drinking water
⇒ Mass Percentage
= 1.5 × 10-3
Calculation of Molality:
⇒ Molecular Mass of Chloroform, CHCl3 =  +  + [35.5 × 3]
= 119.5 g
⇒ Number of Moles of Chloroform = [15 / 119.5]
= 0.1255 moles
= 1.255 × 10-4
Therefore the Mass Percentage is = 1.5 × 10-3 and the Molality of the solution is = 1.255 × 10-4 m.
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