Under what pressure is chloroform at a mercury reading of #940*"Torr"#?

Question

Peyton Adams · Accepted Answer

This is a very poor question, and has been asked by someone who has never used a mercury manometer.

It is a fact that #1# #atm# pressure will support a column of mercury #760# #mm# high. Have you seen a mercury manometer? Mercury has all but disappeared from modern laboratories, on the basis that it is a 100% pain in the posterior to clean up the mercury spills that inevitably occur in the laboratory. For low pressures, a measurement in #mm# of mercury is appropriate. For pressures higher than 1 atmosphere it is completely inappropriate. If you convert the mercury measurement to atmospheres, i.e #"940 Torr"# #=# #940/760*atm#, you have your pressure measurement. Now you have to make another assumption: that all the chloroform is present as a gas. Chloroform has a normal boiling point of #61# #""^@C#. It is unreasonable to propose that it could be present as a gas (by the way, when I say normal boiling point, I mean that its vapour pressure is equal to #1# #atm# at this temperature). I assume this is a first-year undergraduate/second-year physics and chemistry problem? Examiners can also propose bad questions, and students can provide poor answers. As you have probably already realized, this is a real dog's breakfast of a question.

Cooper Adams · Answer

undefined Chloroform at a mercury reading of 940 Torr is under a pressure of 940 Torr.