# Question #36d85

##### 1 Answer

#### Explanation:

The idea here is that a solution's **parts per million** concentration, **ppm**, tells you the number of grams of solute present in exactly

#10^6 = 1,000,000#

parts of solution. Since the mass of the solvent is much, much bigger than the mass of the solute, which I'll assume is the chromium(III) cation, *solution* is **equal** to the mass of the solvent, i.e. of water.

You know that

#2.5 color(red)(cancel(color(black)("L"))) * (1.00color(red)(cancel(color(black)("kg"))))/(1color(red)(cancel(color(black)("L")))) * (10^3color(white)(.)"g")/(1color(red)(cancel(color(black)("kg")))) = 2.5 * 10^3# #"g"#

of water, the solvent. This means that you assume that the mass of the solution is equal to

Now, your solution is **for every**

You can thus say that your solution will contain

#2.5 * 10^3 color(red)(cancel(color(black)("g solution"))) * overbrace("57 g Cr"^(3+)/(10^6color(red)(cancel(color(black)("g solution")))))^(color(blue)("= 57 ppm Cr"^(3+))) = color(darkgreen)(ul(color(black)("0.14 g Cr"^(3+))))#

The answer is rounded to two **sig figs**, the number of sig figs you have for the volume of the solution and for its ppm concentration.