Question

A sample of drinking was found to be contaminated with chloroform. CHCl3 is supposed

to be carcinogen. The level of contamination was 15 ppm (by mass). Express this in %age by

mass. Determine the molality of CHCl3 in water sample​

Answer 1

Answer:

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 percent by mass

(ii) determine the molality of chloroform in the water sample

Explanation:

15 ppm corresponds to 15 g chloroform in 1000,000 g of solution.

(i) Percent by mass =

Mass of solution

Mass of chloroform

×100

Percent by mass =

1000,000

15

×100=1.5×10

−3

%

(ii) Molality =

Molar mass of chloroform ×(Mass of solution−mass of chloroform)

Mass of chloroform

×1000 (all masses in g)

Molality =

119.5×(1000,000−15)

15

×1000=1.255×10

−4

m.

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