Question

Question #745c2

Answer 1

`1.0 * 10^(-4)"g NaCl"`

Explanation:

The thing to remember about concentrations expressed in parts per million is that they are calculated by looking at the number of parts of solute present for every `10^6` parts of solution.

In other words, you're looking for the number of grams of solute present in `10^6` grams of solution. This value will get you the solution's concentration in parts per million.

A `"1 ppm"` solution will thus contain `"1 g"` of solute for every `10^6` `"g"` of solution. Similarly, a `"100.0 ppm"` solution will contain `"100.0 g"` of solute for every `10^6` `"g"` of solution.

Now, you know that your solution must have a concentration of `100.0` ppm and that the mass of the solution is equal to `"1.0 g"`.

Your goal here will be to use the solution's parts per million concentration as a conversion factor to calculate the number of grams of sodium chloride, your solute, needed to make this solution.

`1.0 color(red)(cancel(color(black)("g solution"))) * overbrace("100.0 g NaCl"/(10^6color(red)(cancel(color(black)("g solution")))))^(color(blue)("= 100.0 ppm NaCl solution")) = color(darkgreen)(ul(color(black)(1.0 * 10^(-4)color(white)(.)"g NaCl")))`

The answer is rounded to two sig figs, the number of sig figs you have for the mass of the solution.