Question

A 250-mL aqueous solution contains 1.56 x 10^–5 g of methanol and has a density of 1.03 g/mL. What is the concentration in ppm? A 6.1 X 10^-8 ppmB 1.5 X 1-^-5 ppmC 0.061 ppmD 15 ppm

Answer 1

ppm or part er million is used to measure the concentration of solute in a given volume of solution.

We can calculate it by the formula

`ppm=\frac{mass\text{ of solute \lparen in mg\rparen}}{Volume\text{ of solution \lparen in L\rparen}}_`

In our question we have the next data:

*Mass of methanol

`1.56\text{ }*10^{\frac{-}{}5}g=1.56*10^(-2)mg`

where we have to convert from g to mg.

* The volume of the solution is:

`250\text{ ml = 0.250 L}`

where we have to convert from ml to L

Putin the values on the right-hand side of the equations above we get:

`ppm=\frac{1.56*10^(-5)mg}{0.250\text{ L}}=0.0624`

Looking at the option in the question, by similarity we chose the option c, that is , we chose ppm=0.0611