What are some common mistakes students make when measuring gas pressure?

1 Answer
Jul 5, 2018

Answer:

Given the plethora of gas pressure units...mistakes are routine and inevitable...

Explanation:

One of the things I cannot account for is the persistence of the #"psi"#...#"pounds per square inch"#. What the f... is that? And there is also an issue with #"psi"#, and #"psig"#; the latter is #"pounds per square inch gauge"#, and the ZERO reading on this scale is #1*atm# or #"32 psi"#...And so a reading of #1-2*"psig"# is a bit over one atmosphere.

I think these days the preferred pressure measurement is #"1 bar"#, where #"1 bar"# is almost an atmosphere... Chemists traditionally used the #"atmosphere"#, an accessible and meaningful unit...especially so as a mercury manometer could be set up to measure pressure AT or below #"1 atmosphere..."#

And #1*atm-=760*mm*Hg#... Of course, these days the mercury manometer and the McLeod gauge have all but disappeared from modern laboratories. At least we won't die now!