Calculate the vapor pressure of water at T=90°C

The equilibrium vapour pressure is typically the pressure exerted by a liquid it is A FUNCTION of temperature...

Explanation:

By way of example, chemists and physicists habitually use

P

saturated vapour pressure

...where

P

SVP

is the vapour pressure exerted by liquid water. At

100

∘

C

,

P

SVP

=

1

⋅

a

t

m

. Why?

Well, because this is the normal boiling point of water: i.e. the conditions of pressure (i.e. here

1

⋅

a

t

m

) and temperature, here

100

∘

C

, at which the VAPOUR PRESSURE of the liquid is ONE ATMOSPHERE...and bubbles of vapour form directly in the liquid. As an undergraduate you should commit this definition, or your text definition, to memory...

At lower temperatures, water exerts a much lower vapour pressure...but these should often be used in calculations...especially when a gas is collected by water displacement. Tables of

saturated vapour pressure

are available.