Titration - Manual Procedure

Titration - Manual Procedure

Titration is a procedure in which a solution – called the titrant – whose concentration is known very accurately is dispensed by a burette and reacted with a known volume of another solution of unknown concentration – called the analyte. By measuring the amount of titrant needed to neutralize the analyte, you can determine the concentration of the analyte very accurately.The "end point" of a titration is the point at which the titration is complete, typically when an added indicator solution such as phenolphthalein changes color. The "equivalence point" is closely related to but not necessarily identical with the end point. The equivalence point is the point at which the number of moles (or equivalents) of titrant exactly equals the number of moles (or equivalents) of analyte.Ideally, the end point should exactly equal the equivalence point, but in the real world they are slightly different. For example, you may titrate a hydrochloric acid analyte with a sodium hydroxide titrant, using phenolphthalein as an indicator. Phenolphthalein is colorless in acid solutions, and pink in base solutions, but no color change occurs until the pH of the solution reaches about 8.2, well into the basic range.

Here is the proper way to use a burette:

1. Rinse the inside of a clean burette thoroughly with the solution it will contain. Allow the solution to run out through the stopcock. Drain the burette completely. Repeat the rinse at least once.

2. Make sure the outside of the burette is clean and dry, and then mount it securely to a laboratory ring stand using a burette clamp of the proper size.

3. Fill the burette to above the zero mark, using a graduated cylinder, small beaker, flask or other container. Use a funnel if necessary to prevent spillage.

4. Run some solution through the stopcock to fill the burette tip completely, making sure there are no air bubbles and that the level of the solution falls to or below the zero mark.

5. Record the starting volume. When you complete the titration, you will subtract the starting volume from the final volume to determine the amount of solution you have added. (Read the volume from the bottom of the meniscus).

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