If 18 mL of methanol is used to make an aqueous solution that is 15% methanol by volume, how many mL of solution is produced?

120.0 mL.

Explanation:

As it is known that the no. of millimoles of a solution before dilution is equal to the no. of millimoles after dilution.

We suppose that the initial W% of methanol is 100.0 %

∴ (W%V) before dilution = (W%V) after dilution.

W% before dilution = 100.0 %, V before dilution = 18.0 mL.

W% after dilution = 15.0 %, V after dilution = ? mL.

∴ V after dilution = (W%V) before dilution/W% after dilution = (100.0 %) (18.0 mL) / (15.0%) = 120.0 mL.