Titration mass procent

Question

Hi!

I had a lab on titration to calculate the concentration of acetic acid and from there calculate the mass procent of acetic acid in vinegar.

But I have no idea how to calculate mass procent from concentration please help.

Answer 1

Mass Percent of a solution is found by taking the (Mass of the Solute / Mass of solution ) x 100%

Therefore, in order to calculate mass percent of a solution, you need these 2 pieces of information. The mass of the solute (in this case, acetic acid) and the mass of the solution (in this case, vinegar).

If you weighed your vinegar you have the second piece of information. Or, if you measured volume and are told density, then you can calculate the mass of the solution.

So how do you find the mass of the acetic acid in the vinegar? That comes from the titration experiment. You did a titration with a standard solution of base, I assume. If you know the volume and concentration of your base (most likely NaOH), then you can find the moles of base (NaOH) in the titrant you used.

Then you need to know how these things react. NaOH is a monobasic base (provides one mole of OH- per mole of base) and acetic acid is a monoprotic acid (provides one mole of H+ per mole of acid). These things should react on a 1:1 mole ratio.

CH₃COOH + NaOH --> NaCH₃COO + H₂O

Therefore, if you know your moles of NaOH used, then you know your moles of acetic acid!

If you have the moles, and you have a formula, you can convert the moles to grams (mass!) of acetic acid by using the molar mass (molecular weight). That is the other piece of information you need to find the Mass Percent of acetic acid in the vinegar.

Hope that helps - good luck!