# Question e1635

Nov 27, 2015

Here's what I got.

#### Explanation:

You can think of a $96 : 4$ glacial acetic acid and acetonitrile solution as being equivalent to a 96%"v/v" glacial acetic acid/acetonitrile solution.

In simple terms, you need the target solution to be $96$ parts by volume glacial acetic acid and $4$ parts by volume acetonitrile.

This is equivalent to saying that out of $100$ parts of solution, $96$ will be glacial acetic acid and $4$ acetonitrile.

So, your target solution has a volume of $\text{500 mL}$. In order to keep the above proportions, you would need it to contain

500 color(red)(cancel(color(black)("mL solution"))) * ("96 mL CH"_3"COOH")/(100color(red)(cancel(color(black)("mL solution")))) = color(green)("480 mL") $\text{CH"_3"COOH}$

and

500 color(red)(cancel(color(black)("mL solution"))) * ("4 mL CH"_3"CN")/(100color(red)(cancel(color(black)("mL solution")))) = color(green)("20 mL")# $\text{CH"_3"CN}$

And there you have it. If you mix $\text{480 mL}$ of glacial acetic acid and $\text{20 mL}$ of acetonitrile, you'll get $\text{500 mL}$ of a $96 : 4$ glacial acetic acid/acetonitrile solution.