Sir, how can we convert ppm into any other unit of mass?

ppm is equivalent to part per million by weight.i.e by level of contamination is 15 ppm we mean that if 1 kg of water s taken then content of CHCl₃ is 15 × 10^-6 kg.

Now no. of moles of CHCl₃ = 15 × 10^-3 /119.5=n(let)

then molality = n/(1-15 × 10^-6) 

Putting the value of n we get the molality of chloroform in  solution.