You're performing a titration of some acetic acid. You have reason to doubt that the grocery store is selling you vinegar at the concentration listed on the label. The label says the contents are 2.00M acetic acid. You begin performing the titration on 5mL of the acetic acid sample with 0.42M NaOH. You perform the titration and find that your indicator (phenolphthalein) turns the slightest shade of pink and determine you've added 45.7mL of the 0.42M NaOH.

Question

You're performing a titration of some acetic acid.  You have reason to doubt that the grocery store is selling you vinegar at the concentration listed on the label.  The label says the contents are 2.00M acetic acid. You begin performing the titration on 5mL of the acetic acid sample with 0.42M NaOH.  You perform the titration and find that your indicator (phenolphthalein) turns the slightest shade of pink and determine you've added 45.7mL of the 0.42M NaOH.

What is the concentration of the acetic acid purchased from the grocery?

DrBob222 · Answer

Acetic acid is CH3COOH which I will write as HAc. The titration equation is
HAc + NaOH ==> NaAc + H2O
mols NaOH used = M x L = 0.42 M x 0.0457 = 0.0192
mols HAc titrated = 0.0192
M HAc = mols HAc/mL HAc = 0.0192/0.005 L = 3.84 M
I'd say you got your money's worth.