# What is the %m/m of 75.0 g of ethanol dissolved in 500.0 g of water?

##### 1 Answer

#### Explanation:

By definition, a solution's **percent concentration by mass**,

This means that if you know the number of grams of ethanol dissolved in exactly

Now, you know that your solution contains **total mass** of the solution is equal to

#"75.0 g " + " 500.0 g" = "575.0 g"#

So you can say your

This means that

#100 color(red)(cancel(color(black)("g solution"))) * "75.0 g ethanol"/(575.0 color(red)(cancel(color(black)("g solution")))) = "13.043 g ethanol"#

Since this represents the number of grams of ethanol present per **percent concentration by mass** is equal to

#color(darkgreen)(ul(color(black)("% m/m = 13.0% ethanol")))#

The answer is rounded to three **sig figs**, the number of sig figs you have for the mass of ethanol.