The Use of Volumetric Glassware

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CHEM 1411
Summer 2012
Dr. Rodriguez
By: Victor Dominguez

Short description of the lab and it importance. Answer three questions a. What did you do?
In this experiment we were exposed to a variety of important concepts related to quantitative experimentation, including the proper use of glassware, and analytical balances. b. How did you do it? Briefly describe the procedures in 1 sentence. We calibrate a volumetric pipet and flask. We also calibrated a beaker and 50 mL buret. We also calculate the difference between the expected density and density obtained by our team. c. What happened? Briefly give the result (or results) of the experiment in 1 sentence. We noticed the calibration marks on the beakers were taken only to be an approximate guide to volume because the marks were placed at greater intervals. This did not allow for precise measurements. The 25-mL volume dispensed by the pipet was much more precise than using the beaker and more precise than the graduated cylinder as well Pre-Lab:

1. Pipets used for the transfer of samples of aqueous solutions are always rinsed with a small portion of the solution to be used before the sample is taken. Calculate the percentage error arising in an experiment when 1-mL, 5-mL, and 10-mL pipets are used for transfer and each pipet contains 5 drops of water adhering to the inside of the barrel. A single drop of water has an approximate volume of 0.05 mL.

5*0.05 = 0.25 mL is the volume of water in the pipet

error for the 1 mL pipet = 0.25*100/1 = 25%
error for the 5 mL pipet = 0.25*100/5 = 5%
error for the 10 mL pipet = 0.25*100/10 = 2.5%
2. It is important to make certain that there is no air bubble in the tip of the buret below the stopcock before the initial reading of the liquid level in the buret is taken. If a 0.5-mL air bubble is present in the tip of a buret, what percent error in 10-mL, 20-mL, and 40-mL samples will result if the air bubble is dislodged...
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