what sample size of .9181M vinegar would require 27.50 mL of .5185M of NaOH for neutralization?

Answer 1

How many moles NaOH do you have? That is M x L = ??
How many moles vinegar do you have? That will be the same as the number of moles NaOH since the equation is a 1:1 ratio.
CH3COOH + NaOH ==> H2O + CH3COONa
Then M vin = moles vin/L vin and solve for L vinegar.

Answer 2

Thanks Dr.Bob!