How do you prepare a sample for acid-base titration?

To prepare a sample for acid-base titration, you need to accurately measure and dilute the sample, then add an indicator.

In more detail, the first step in preparing a sample for acid-base titration is to accurately measure the sample. This is typically done using a pipette, which allows for precise measurement of the sample volume. The sample is then transferred to a clean, dry conical flask.

Next, the sample needs to be diluted. This is done by adding a known volume of distilled water to the flask. The exact volume of water required will depend on the concentration of the sample and the desired concentration for the titration. It's important to remember that the volume of water added does not affect the amount of substance in the sample, it only changes the concentration.

Once the sample has been diluted, an indicator needs to be added. The indicator is a substance that changes colour when the solution changes from acidic to basic, or vice versa. This colour change signals the end point of the titration, which is the point at which the amount of acid equals the amount of base. The choice of indicator depends on the pH at the equivalence point of the titration. Common indicators include phenolphthalein, which turns from colourless to pink as the solution becomes basic, and methyl orange, which turns from red to yellow as the solution becomes acidic.

Finally, the prepared sample is ready for the titration. The titrant (the solution of known concentration) is slowly added to the sample while stirring until the end point is reached, as indicated by the colour change of the indicator. The volume of titrant used gives the information needed to calculate the concentration of the unknown solution.

Remember, safety is paramount when handling acids and bases, so always wear appropriate protective equipment and work in a well-ventilated area.