What pressure IN #"kilopascals"# is exerted by the DRY gas if it is has been collected over water at #75# #""^@C#, and the total pressure is #3.41*atm#?

1 Answer
anor277
Apr 27, 2017

You need to quote the #"saturated vapour pressure"# for an accurate answer.

Explanation:

The pressure exerted by gases ABOVE an aqueous phase is equal to the SUM of the pressure of the individual gases, and the so-called #"saturated vapour pressure"# that the water molecules exert. That this must be considered in the problem is indicated by the specific wording; they specify a #"dry gas"#.

At #75# #""^@C#, #"= SVP = 0.3806"*"atm"#. These data are taken from this site. What is #"SVP"# at #100# #""^@C#?

And so #P_"measured"=P_"gas"+P_"SVP"#, and............

#P_"Gas"=P_"measured"-P_"SVP"=(3.41-0.3806)*atm=3.029*atm#.

And so, since #1*atm-=101.3*kPa#, then...........

#P_"gas"=3.029*atmxx101.3*kPa*atm^-1~=303*kPa#.

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