Question

Calculate the mass of `KCl` that should be dissolved to form a 5 ppm `Cl^-` ion solution having a total volume of 20 `dm^3`?

Answer 1

The mass of KCl is 0.2 g.

Explanation:

`"5 ppm"` means `"5 g of solute"` in `10^6 "g of solution"`.

`"Mass of soln" = 20 cancel("dm³ soln") × "1000 g soln"/(1 cancel("dm³ soln")) = "20 000 g soln"`

`"Mass of Cl"^(-) = 20 000 cancel("g soln") × ("5 g Cl"^-)/(10^6 cancel("g soln")) = "0.10 g Cl"^-`

`"Mass of KCl" = 0.10 cancel("g Cl⁻")× "74.55 g KCl"/(35.45cancel("g Cl⁻")) = "0.2 g KCl"`