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.](https://en.wikipedia.org/wiki/Vapour_pressure_of_water) What is SVP at 100 ∘C?

And so Pmeasured=Pgas+PSVP, and............

PGas=Pmeasured−PSVP=(3.41−0.3806)⋅atm=3.029⋅atm.

And so, since 1⋅atm≡101.3⋅kPa, then...........

Pgas=3.029⋅atm×101.3⋅kPa⋅atm−1≅303⋅kPa.

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