Question 474ca

Nov 16, 2015

47.1%

Explanation:

The idea here is that you need to use the density of the solution to find its mass. Once you know its mass, you can determine the percent concentration by mass by using the mass of the solute.

So, density is defined as mass per unit of volume. In your case, a density of $\text{1.15 g/mL}$ means that you get $\text{1.15 g}$ for every $\text{1 mL}$ of solution.

In this case, the mass of the solution will be

1.00color(red)(cancel(color(black)("L"))) * (1000color(red)(cancel(color(black)("mL"))))/(1color(red)(cancel(color(black)("L")))) * "1.15 g"/(1color(red)(cancel(color(black)("mL")))) = "1150 g"

Now, the solution's percent concentration by mass is defined as the mass of the solute divided by the mass of the solution, and multiplied by $100$

$\textcolor{b l u e}{\text{%w/w" = "mass of solute"/"mass of solution} \times 100}$

Plug in your values to get

"% w/w" = (542color(red)(cancel(color(black)("g"))))/(1150color(red)(cancel(color(black)("g")))) xx 100 = color(green)("47.1%")#

This means that every $\text{100 g}$ of solution will contain $\text{47.1 g}$ of solute.