# Question #fbe14

##### 1 Answer

#### Explanation:

The trick here is to realize that a solution's mass by mass percent concentration, **of solution**.

The mass of the solution will be equal to the sum of the mass of the solute and of the mass of the solvent

#"mass of solution = mass of solute + mass of solvent"#

In your case, you will have

#"mass of solution" = "4.6 g" + "250 g" = "254.6 g"#

Now, you know that this solution contains

As you know, solutions are homogeneous mixtures, which implies that they have the same composition throughout.

This allows you to use the known composition of the solution as a **conversion factor**

#100 color(red)(cancel(color(black)("g solution"))) * overbrace("4.6 g NaCl"/(254.6 color(red)(cancel(color(black)("g solution")))))^(color(blue)("the composition of the solution")) = "1.807 g NaCl"#

You can thus say that the solution's mass by mass percent concentration is equal to

#color(darkgreen)(ul(color(black)("% m/m = 1.8% NaCl")))#

The answer is rounded to two **sig figs**, the number of sig figs you have for the mass of sodium chloride and for the mass of water.