# Question a939a

May 20, 2017

$\text{26% NaCl}$

#### Explanation:

The problem wants you to calculate the percent concentration by mass, $\text{% m/m}$, of sodium chloride in this solution.

The key thing to remember here is that a solution's percent concentration by mass tells you the mass of solute, which in your case is sodium chloride, present for every $\text{100 g}$ of solution.

After you dissolve the sodium chloride, the mass of the solution will be

${m}_{\text{solution" = "36 g" + "100 g" = "136 g}}$

You know that you have $\text{36 g}$ of sodium chloride in $\text{136 g}$, so use this as a conversion factor to find the mass of sodium chloride present in $\text{100 g}$ of solution

100 color(red)(cancel(color(black)("g solution"))) * "36 g NaCl"/(136color(red)(cancel(color(black)("g solution")))) = "26.47 g NaCl"

This means that the solution's percent concentration by mass is

color(darkgreen)(ul(color(black)("% NaCl" = 26%)))#

The answer is rounded to two sig figs.