An acid titration is a chemical procedure designed to determine the concentration of an unknown acid. Before starting the titration, use a piece of litmus paper to estimate the pH of the acid. A basic solution with a known concentration is used to neutralize the acidic solution.
What You Need
To perform an acid titration, you will need a burette, beaker, indicator solution, unknown acid and known base. Depending on the pH of the solution, which is indicated by litmus paper, chose an indicator that fits that pH range. For example, if you estimate the pH of the acid to be about 5, you would want to use bromocresol green. Record the amount of acid you pour into the beaker and the amount of base you pour into the burette. Drop a few drops of the indictor into the beaker.
Procedures
When you have set up the experiment, begin to slowly drip the base into the acid. Each indicator changes different colors. For example, bromocresol green will change from yellow to blue when it goes from an acid to a base. Right as the indicator begins to change, stop dripping the basic solution into the acid. The experiment is complete. If you are not sure if it has changed, record the volume of base left in the burette and then add another drop. If the color completely changes, you have gone too far.
Results
When the indicator has shown that the titration is complete, determine the amount of base added by subtracting the amount of liquid left in the burette from the amount that it originally contained. Multiply this volume by the concentration of the base. Then divide by the volume of the acid in the beaker. The result is the concentration of the acid. For example, if you started with 50 milliliters of base and at the end of the experiment the burette only contains 30 milliliters, you could determine that 20 milliliters were used. If the concentration of the base were 1.2 M, you would multiply that by 20 and get 24. If there were originally 48 milliliters of acid in the beaker, you would divide 24 by 48 and find the concentration of the acid to be 0.5 M.
Tags: acid beaker, acid titration, amount base, basic solution, bromocresol green, concentration acid