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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. |
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Answer» SOLUTION : 15 ppm means 15 parts in one million` (10^6) ` parts by mass in the solution ` therefore ` PERCENTAGE by mass = `(15)/(10^6) xx 100 = 15 xx 10^(-4)` Taking 15 g chloroform in `10^6` g of the solution, mass of solvent`~~10^6 g`[Neglecting 15 in COMPARISON with `10^6`] Molar mass of `CHCl_3 = 12 + 1 + 3 xx 35.5 = 119.5 g "mol"^(-1)` molality ` = (15// 119.5)/(10^6) xx 1000 = 1.25 xx 10^(-4) m` |
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