Household vinegar is a solution of acetic acid (HCH3COO) in water. Most vinegars contain 5% acetic acid by volume. What volume of acetic acid is present in a 0.250 L bottle of vinegar?

12.5 mL of acetic acid

Explanation:

The % by volume indicates the volume of solute in 100mL of solution.

It is a common type of concentration, as percent by mass or molarity.

Our solution is made of vinegar

Our solute is the acetic acid.

(Volume of solute / Volume of solution) . 100 = 5

(Volume of solute / 0.250L) . 100 = 5

(Volume of solute / 0.250L) = 0.05

Volume of solute = 0.05 . 0.250L → 0.0125 L

We convert the volume to mL→ 0.0125 L . 1000 mL /1L = 12.5 mL

We can also see this problem by a rule of three:

We convert the 0.250L to mL → 250 mL

And we propose, if 100 mL of vinegar have 5mL of acetic acid

250 mL may have (250 . 5) / 100  =  12.5mL