# Question 8b2b6

Feb 20, 2017

Here's what I got.

#### Explanation:

We usually reserve parts per million to express very, very small concentrations of solute, sometimes called trace amounts, in a given solution, but you can pretty much use parts per million to express any concentration if you want.

A concentration of $\text{1 ppm}$ corresponds to $1$ part solute present for every ${10}^{6}$ parts solution. To find a solution's concentration in parts per million, you can use the equation

$\textcolor{b l u e}{\underline{\textcolor{b l a c k}{\text{ppm" = "grams of solute"/"grams of solution} \times {10}^{6}}}}$

If you take water's density to be approximately equal to ${\text{1.0 g mL}}^{- 1}$, then you can say that your solution will contain

1000 color(red)(cancel(color(black)("mL"))) * "1.0 g"/(1color(red)(cancel(color(black)("mL")))) = "1000 g"

After you mix the solute and the solvent, you will end up with

${m}_{\text{solution" = "400 g" + "1000 g" = "1400 g}}$

This means that the solution will have a concentration of

(400 color(red)(cancel(color(black)("g"))))/(1400color(red)(cancel(color(black)("g")))) xx 10^6 = color(darkgreen)(ul(color(black)(3 * 10^5color(white)(.)"ppm")))#

The answer is rounded to one significant figure.

As you can see, it's not very practical to use parts per million for such concentrated solutions.