Chemists perform titrations to determine the amount of an unknown substance that is in a solution. In an acid/base titration, a chemist determines the unknown pH of a solution by slowly adding a strong base--or acid to an acidic--or alkaline solution until it becomes neutral. The chemist can then calculate the pH of the original solution by how much strong acid or base that was required to neutralize it. Normally, indicator chemicals that change color as pH changes are used to show the chemist when the solution has been neutralized, but a pH meter can be used for the same purpose. It should be said, though, that using a pH meter will take more time, as it does not generate readings as quickly as an indicator changes color.
Instructions
1. Set up your titration like you normally would: clamp the burette to a stand and fill it with the strong acid or base you will be using to titrate the sample. Place a sample of your unknown acid or base in a 50 milliliter (mL) beaker and place it underneath the burette. Since you are using a pH meter to detect the equivalence point, you will not need to add an indicator chemical to the sample.
2. Loosen the valve on the burette and allow the strong acid or base to drip slowly into the sample as you swirl it in the beaker.
3. Insert the electrode of your pH meter in the sample and take periodic pH readings as you titrate the sample. The readings should become more frequent as they approach the equivalence point--a pH of 7.0--so that you don't miss it.
4. When the pH meter reads 7.0, stop titrating. Look at the burette to determine how much strong acid or based you used to reach the equivalence point, and calculate the pH of the original solution as you normally would if you had used a chemical indicator.
Tags: acid base, strong acid, strong acid base, calculate original, calculate original solution, equivalence point