BEHS Chemistry

Your Basic Acid-Base Titration

When acids and bases are mixed together, they will NEUTRALIZE the effect of each other.

Acid + Base -> Water + Salt

This fact can be used to determine the H + or OH - concentration of an UNKNOWN solution. This process is done by means of titration.

TITRATION is the incremental addition of acid (or base) to a solution of base (or acid) so the progress of the neutralization reaction can be monitored with an indicator.

After titrating until the pH of 7 (neutral) is reached, you can calculate the amount of acid or base in an unknown sample if you know the VOLUME and concentration of the solution you titrate the unknown sample with:

Volume acid x Molarity acid = Volume base x Molarity base

A simple acid base titration is illistrated in the following video clip. Bromthymal blue indicator is added to a beaker full of Hydrocloric acid. Bromthymal blue turns yellow in the presence of an acid, and blue when it is in a basic solution. The point at which it changes from yellow to blue is around a pH of 7.

The original volume of the acid was 100 ml, the concentration was unknown. From the titration I know that it took 48 ml of 1 molar NaOH to neutralize the acid. With these numbers I am ready to calculate the unknown acid concentration.

Volume acid x Molarity acid = Volume base x Molarity base
-----100ml----- x -------?----------= -----48ml ----- x -----1 M

48 ml M / 100 ml = .48 M
The concentration of the unknown solution is roughly .5 M.


Click to view a graph of a titration. The graph shows the graph of pH
verses volume. You must have logger pro 3.3 to view view this graph.






Contact: Tom Davidson, Box Elder High School 380 So. 600 w. (435-734-4840) Email: