# Question 10e83

Oct 12, 2016

$\text{25 g}$

#### Explanation:

A $\text{10.0% w/v}$ solution contains $\text{10.0 g}$ of solute, which in your case is sodium chloride, for every $\text{100 mL}$ of solution.

In other words, if you take a $\text{100 mL}$ sample of this solution you will end up with $\text{10.0 g}$ of sodium chloride, dissolved in solution, of course.

You are told that the volume of the solution is equal to $\text{250 mL}$. Since you know that you get $\text{10.0 g}$ of sodium chloride per $\text{100 mL}$ of solution, you can say that the given sample must contain

250 color(red)(cancel(color(black)("mL solution"))) * overbrace("10.0 g NaCl"/(100color(red)(cancel(color(black)("mL solution")))))^(color(blue)(="10.0% w/v")) = color(green)(bar(ul(|color(white)(a/a)color(black)("25 g NaCl")color(white)(a/a)|)))#

The answer is rounded to two sig figs.

So, in order to make your solution, you should dissolve $\text{25 g}$ of sodium chloride in $\text{100 mL}$ of water, then add enough water to get the final volume to $\text{250 mL}$.