How is the procedure to prepare a buret or volumetric pipette to avoid contamination different than preparing a reaction flask or a volumetric flask? Which procedure is employed to prepare the cu- vette that is used in the spectrophotometer? (Hint: think about the rinses you should do to prepare these instruments.)

To avoid contamination in laboratory glassware, different procedures are employed for preparing a buret, volumetric pipette, reaction flask, volumetric flask, and cuvette. Here’s a detailed breakdown of the procedures for each: ### 1. Buret and Volumetric Pipette Preparation **Procedure:** - **Rinsing with Solvent:** - Rinse the buret or volumetric pipette with the solution that will be used in the experiment. This is crucial to ensure that any residual contaminants from previous uses are removed and that the glassware is conditioned with the solution to be measured. - For a buret, fill it with the solution, let it sit for a few seconds, and then drain it out. Repeat this process 2-3 times. - For a volumetric pipette, draw the solution into the pipette and then expel it. Repeat this process 2-3 times. - **Final Fill:** - After rinsing, fill the buret or volumetric pipette with the solution to the desired level for use in the experiment. ### 2. Reaction Flask and Volumetric Flask Preparation **Procedure:** - **Rinsing with Solvent:** - Rinse the reaction flask or volumetric flask with distilled water to remove any contaminants. This is especially important if the flask has been used previously. - After rinsing with water, rinse the flask with the solution that will be used in the experiment. This is similar to the procedure for the buret and pipette but may not require multiple rinses if the flask is clean. - **Final Fill:** - For a volumetric flask, after rinsing, fill it to the mark with the solution to achieve the desired concentration. ### 3. Cuvette Preparation for Spectrophotometer **Procedure:** - **Rinsing with Solvent:** - Rinse the cuvette with the solution that will be analyzed. This is important to ensure that the optical path is clean and free from contaminants that could affect the absorbance readings. - Fill the cuvette with the solution, then discard it, and repeat this process 2-3 times to ensure thorough rinsing. - **Final Fill:** - After rinsing, fill the cuvette with the solution to be measured, ensuring that there are no bubbles and that the optical surfaces are clean. ### Summary of Differences - **Buret and Volumetric Pipette:** Focus on rinsing with the solution to be used, ensuring that the glassware is conditioned with that specific solution. - **Reaction Flask and Volumetric Flask:** Rinse with distilled water first, then with the solution, but the emphasis is more on cleaning than conditioning. - **Cuvette:** Rinse with the solution to be analyzed, ensuring that the optical surfaces are clean for accurate spectrophotometric measurements. By following these procedures, contamination can be minimized, ensuring accurate and reliable experimental results.