# Question #865b5

##### 1 Answer

Here's what I got.

#### Explanation:

In order to find the solution's **percent concentration by mass**,

You know that a sample of this solution contains

I will assume that the *pure solvent* has a density of

#50 color(red)(cancel(color(black)("mL"))) * "0.7 g"/(1color(red)(cancel(color(black)("mL")))) = "35 g"#

So, the sample contains

#"5 g + 35 g = 40 g"#

of the solution, which means that

#100 color(red)(cancel(color(black)("g solution"))) * "5 g solute"/(40color(red)(cancel(color(black)("g solution")))) = "12.5 g solute"#

Therefore, you can say that the solution's percent concentration by mass is equal to

#color(darkgreen)(ul(color(black)("% m/m = 12.5%")))#

I'll leave the answer rounded to three **sig figs**, but keep in mind that you should report the answer as

#"% m/m = 10%"#

because you have only one significant figure for your values.