Acid-Base Titration Calculation

It's a neutralization reaction to figure acid or base concentration

A titration is used to determine concentration of an acid or base.
A titration is used to determine concentration of an acid or base. Sandra Mu/Getty Images

An acid-base titration is a neutralization reaction performed in the lab to determine an unknown concentration of acid or base. The moles of acid will equal the moles of base at the equivalence point. So, if you know one value, you automatically know the other. Here's how to perform the calculation to find your unknown:

Acid-Base Titration Problem

If you're titrating hydrochloric acid with sodium hydroxide, the equation is:

HCl + NaOH → NaCl + H2O

You can see from the equation there is a 1:1 molar ratio between HCl and NaOH. If you know that titrating 50.00 ml of an HCl solution requires 25.00 ml of 1.00 M NaOH, you can calculate the concentration of hydrochloric acid, HCl. Based on the molar ratio between HCl and NaOH, you know that at the equivalence point:

moles HCl = moles NaOH

Acid-Base Titration Solution

Molarity (M) is moles per liter of solution, so you can rewrite the equation to account for molarity and volume:

MHCl x volumeHCl = MNaOH x volumeNaOH

Rearrange the equation to isolate the unknown value. In this care, you are looking for the concentration of hydrochloric acid (its molarity):

MHCl = MNaOH x volumeNaOH / volumeHCl

Now, simply plug in the known values to solve for the unknown:

MHCl = 25.00 ml x 1.00 M / 50.00 ml

MHCl = 0.50 M HCl