# Relationship of vapour pressure and Dew Point

1. Apr 1, 2014

1. The problem statement, all variables and given/known data
Moist air at 32 degrees C has a dew point of 26 degrees C. The total or atmospheric pressure
is 100.7kPa.

find the:
Molal Humidity
Relative Humidity
2. Relevant equations
Molal Humidity = $\frac{P_{i}}{P_{tot} - P_{i}}$
Relative Humidity = $\frac{P_{i}}{P_{vap}}$

3. The attempt at a solution
I'm thinking I can simply sub in the vapour pressure for the dew point (looking at a pressure table) straight in as the partial pressure for molal humidity.

I got an answer of 3.45%, using equation for molal humidity. I have no answers for this particular question, so I'm not sure if this is correct.

2. Apr 1, 2014

### Staff: Mentor

Looks correct.

Chet