A 250 mL sample of oxygen is collected over water at 25°C and 760.0 torr pressure. What is the pressure of the dry gas alone?

1 Answer
anor277
Apr 29, 2016

You need to know the #"saturated vapour pressure"# of water at #25# #""^@C#.

Explanation:

The gas collected over water consists of (i) whatever the gas is, and (ii) the saturated vapour pressure. At #25# #""^@C#, #"SVP"# #=# #23.8# #mm*Hg#. At higher temperatures, how would you expect #"SVP"# to evolve.

Thus the pressure exerted by the gas is thus #(760-23.8)*mm*Hg#.

#"SVP"# would always be given in such a problem.

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