Question

A chemist needs to make an acidic solution that is 0.25 M in acetic acid (HC 2 H 3 O 2 ). If she plans to prepare 250mL of solution, how much acetic acid must she use to prepare the solution.

Answer 1

15g

Step-by-step explanation:

Molar mass of acetic acid = 60g/mol

Molarity = mass ÷ molar mass

mass = 0.25 × 60

= 15g

∴ 15g of acetic acid weighed into 1L volumetric flask would give 0.25M of acetic acid.

Alternatively, if the solution is being prepared from a stock solution of known concentration, (say 500mL of 0.5M solution), the formular C2V1 =C2V2 can be used to find the dilution volume.