Piece Precision
Posted on Sunday, March 7th, 2010 at 5:41 pmBeaker vs Flask?
can someone give me estimates on this...I cant really find many sites comparing the 2 and when one should be used over the other. I figured the only reason to use a flask would be if you need to stopper it and mix. And im not sure about their percisions.
Question 2. Examine a 250 mL beaker available in your drawer. Compare the precision of these pieces
of equipment with that of a graduated cylinder, pipette and buret. What is the maximum precision that can
be achieved by using the beaker and the flask? (example: nearest 10 mL, nearest 1 mL, nearest 0.1 mL,
nearest 0.01 mL etc). When should a beaker or Erlenmeyer flask be used to measure volumes?
1. You would use a flask when you expect a gas to be emitted and collected as in distillation or a gas-producing reaction, or when you simply want to stopper it to keep the contents clean and prevent evaporation loss. If collecting an emitted gas you would use a 1-holed stopper and tubing. In some experiments a gas is passed into the flask and processed in some way in the flask, and the resulting gaseous product is collected; this would require a 2-holed stopper. Another use of a 2-holed stoppered flask would be to collect the liquid from a filter or separatory funnel, and to let out the displaced gas.
2. The precision of a flask is better than that of a beaker when the liquid comes up to the neck section where a small volume difference results in a larger height change. Assume you can read the liquid level to 0.05 inch, and that the liquid surface area in the beaker is 12 in^2 and that in the flask neck is 1.2 in^2. Then the best precision you can expect from the beaker would be 0.6 in^3 or about 10 ml whereas at the neck of the flask the precision would be about 1 ml.
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