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TechnoratiHELP ME!! THANK YOU!!!
Submitted by Anonymous on 27 February 2006 - 8:20pm.
I'm about 35 yrs of age and trying to get into Dental school.
Please help me on my chemistry lab.
Q. #1 Why do we never pipet "by mouth" in the chemistry lab?
Q. #2 What is the source of the MERCURY? Where can we get it? How can we purify the mercury?
Q. #3 It is important to make certain that there is no air bubble in the tip of a buret below the stopcock before the initial reading of the liquid level in the buret is taken. Explain why the tip of the buret must contain liquid, and no air bubbles.
Thank you so much in advance.
1) Because of the likelyhood of overpipeting, thus putting some of the pipeted fluid inside your mouth. The consequences of this may vary between pipeting errors to death, depending on the fluid and the amount ingested.
2) Mercury is mined as mercuris sulphide (HgS). It is heated to about 540º; mercury evaporates, and is condensed as metal mercury (Mg0). This is also applyable as a low-grade purification method. It can be furtherly refined, I think, via electrolisis.
3) The measures taken with a buret depends on the volume of liquid dropped from it. If the buret contains bubbles, they will probably escape to atmosphere, thus causing an excess error.