Hello, Michael,
It is imporant to note the balanced chemical equation for this reaction. We can then tell the mole ratio of NaOH to acetic acid. In this case we see that it is 1 mole NaOH to 1 mole of acetic acid. So if we have a mole of one, we'll need a mole of another for complete neutralization.
We can determine the number of moles of substance by multiply the volume times the concentration (in liters and M). 1 M means 1 mole/liter.
We can use the expression M1V1 = M2V2 to determine the number of moles that will be equal to what we know. M is molarity and V is volume for solutions 1 and 2.
Let M2V2 be the volume and concentation of acetic acid: (20ml and 0.1M).
We can leave the volume units as ml, which means the answer will be in ml. We could also convert to liters, but lets leave it in ml, since that is the unit requested. V1 is the unknown volume of NaOH, and M1 is 0.15M.
(0.15M)*(V1) = (0.1M)*(20ml)
V1 = ((0.1M)*(20ml))/(0.15M)
V1 = 13.3 ml.
Bob
