# Question #9356d

##### 1 Answer

#### Explanation:

This one is pretty straighforward - all you have to do is **not** get distracted by the fact that you're mixing the ethanol solution with a methanol solution and not with pure water.

A solution's percent concentration by volume is defined s the volume of the solute divided by the **total volume of the solution**, and multiplied by

#"% v/v" = "volume of solute"/"volume of solution" xx 100#

In your case, a **for every**

Calculate what volume of ethanol you have in your

#75color(red)(cancel(color(black)("mL solution"))) * "25 mL ethanol"/(100color(red)(cancel(color(black)("mL solution")))) = "18.75 mL"#

Now, you mix this sample with a

As far as the concentartion of ethanol is concerned, all you need to focus on here is what the **total volume of the resulting solution** will be.

#"75 mL" + "25 mL" = "100 mL"#

The final solution has avolume of **remaind unchanged**, it follows that the new percent concentration by volume of ethanol will be

#"% v/v" = (18.75color(red)(cancel(color(black)("mL"))))/(100color(red)(cancel(color(black)("mL")))) xx 100 = 18.75%#

Round this to two sig figs to get

#"% v/v" = color(green)("19%")#