# A 4.33 g sample of a laboratory solution contains 1.32 g of acid. What is the concentration of the solution as a mass percentage?

##### 1 Answer

#### Explanation:

A solution's *percent concentration by mass*, **of solution**.

#color(blue)(|bar(ul(color(white)(a/a)"% m/m" = "grams of solute / 100 g of solution"color(white)(a/a)|)))#

As you know, a solution contains a solute and a **solvent**, which more often than not is water. This means that a solution's **grams of solute** and **grams of solvent** must be mixed to get

In your case, you know that you get **of solution**. To find the solution's percent concentration by mass, use this as a conversion factor to figure out how many grams of solute you'd get in

#100 color(red)(cancel(color(black)("g solution"))) * overbrace("1.32 g acid"/(4.33color(red)(cancel(color(black)("g solution")))))^(color(purple)("given to you")) = "30.5 g acid"#

Since

#"% m/m" = color(green)(|bar(ul(color(white)(a/a)color(black)("30.5% acid")color(white)(a/a)|)))#

The answer is rounded to three **sig figs**.

Notice that this is equivalent to dividing the mass of solute by the **total mass of the solution** and multiplying by

#"% m/m" = (1.32 color(red)(cancel(color(black)("g acid"))))/(4.33color(red)(cancel(color(black)("g solution")))) * 100 = color(green)(|bar(ul(color(white)(a/a)color(black)("30.5% acid")color(white)(a/a)|)))#

As mentioned before, you can use the solution's percent concentration by mass to say that

#"30.5 g acid"" "# and#" " "100 g " - " 30.5 g" = "69.5 g water"#

In other words, you can make this solution by adding **for every** **per** **of solution**.