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Relationship of vapour pressure and Dew Point

  • Thread starter miniradman
  • Start date
  • #1
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Homework Statement


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

Homework Equations


Molal Humidity = [itex]\frac{P_{i}}{P_{tot} - P_{i}}[/itex]
Relative Humidity = [itex]\frac{P_{i}}{P_{vap}}[/itex]


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.
 

Answers and Replies

  • #2
19,676
3,987

Homework Statement


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

Homework Equations


Molal Humidity = [itex]\frac{P_{i}}{P_{tot} - P_{i}}[/itex]
Relative Humidity = [itex]\frac{P_{i}}{P_{vap}}[/itex]


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.
Looks correct.

Chet
 

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