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A sample of drinking water was found to ...

A sample of drinking water was found to be severely contaminated with chloroform, `CHCl_(3)`, supposed to be carcinogen. The level of contamination was 15 ppm (by mass).
(i) Express this in per cent by mass.
(ii) Determine the molality of chloroform in the water sample.

Text Solution

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15 ppm means 15 parts in million `(10^(6))` by mass in the solution
`therefore`Percentage by mass `=(15)/(10^(6))xx100=15xx10^(-4)%`
As only 15g of chloroform is present in `10^(6)g` of the solution, mass of the solvent`=10^6g`
Molar mass of `CHCl_(3)=12+1+3xx35*5`
`=119*5" g "mol^(-1)`
Moles of `CHCl_(3)=(15)/(119*5)`
`therefore"Molarity"=(15//119*5xx1000)/(10^(6))=1*25xx10^(-4)m`
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