Question

A given sample of drinking water was found to be severely contaminated with Chloroform (${\mathrm{CHCl}}_3$) supposed to be a carcinogen. The level of contamination was 15 ppm by mass. Answer the following questions: Determine the Molality of Chloroform in the water sample.

Answer 1

Given: $\left[{\mathrm{CHCl}}_3\right]=15\mathrm{ppm}$

Step: 1 Introducing the formula for calculating molality

$Molality=\frac{No.ofmolesofsolute}{Massofsolution\left(Kg\right)}$

Step: 2 Calculating the molality of the solution

The molar mass of chloroform is 119.5 g/mol

$$\begin{gathered} Molality=\frac{15}{119.5\times ({10}^6-15)}\times 1000=\frac{15}{119.5\times \left({10}^6\right)}\times 1000 \\ Molality=\frac{15}{119.5}\times {10}^{-3}=0.125\times {10}^{-3} \\ Molality=\frac{15}{119.5}\times {10}^{-3}=1.25\times {10}^{-4} \end{gathered}$$

Therefore, the molality of the solution is $1.25\times {10}^{-4}$m.