Question

How would i figure out the vapor pressure at room temperature?
(atmospheric pressure is 760 mm hg and the temperature is 20C.)

Answer 1

If you want the vapor pressure of water at 20 degrees C, you look it up in a set of tables. Almost every chemistry or physics text has a set of vapor pressures at various temperatures for water. If it's something besides water, and you know the delta Hvap, you use the Clausius-Clapeyron equation.