Vapor pressure of Water calculation

In summary, the conversation revolved around calculating the vapor pressure of water at 43.0°C with the given information of the total pressure of the system being 758.3 torr. The equation P(water vapor) = P(total) - P(air) was discussed, along with the confusion surrounding the equation ln P = -(H/R)(1/T) + ln A. The question of how to determine the pressure of air at 43°C was also brought up, with the mention of looking for information online or in thermo books. The conversation ended with a link provided for further help on the topic.
  • #1
jKotha
30
0
Ok, I need to calculate the vapor pressure of water.

All the information I am given is that the temp is 43.0 C, and I know the total pressure of the system is 758.3 torr.

Is there anyway I can calculate this using the Pwater = Ptotal - Pair equation?
There is also another equation that I have, but it is quite confusing for me. It is ln P = -(H/R)(1/T) + ln A

PLEASE HELP! Thanks guys

Jkotha
 
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  • #2
If air is covering the water, then the gas phase contains air and water vapor, therefore P(water vapor) = P(total) - P(air).

Then what is the pressure of air at 43°C? For interest sake, what is the saturation pressure of water vapor at 43°C?
 
  • #3
still not gettin it..

Ok i know that Ptotal = Pair + Pwater..

but... How do I know what Pair is at 43 C? That is the problem. Is there some standard definition of the pressure of air at a given temperature? I'm not sure... If I had that information it would make this problem a snap.

thanks,
jkotha
 
  • #4
I thought I could find it online, but that doesn't seem to be easy.

I'll look in some thermo books, but that will have to wait until morning.

The interesting thing is that the total pressure of 758.3 torr is less than standard pressure for 760 torr, which I would expect for 43°C.

See if this helps - http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/dvlp/rh.rxml
 
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1. What is vapor pressure?

Vapor pressure is the pressure exerted by the gas phase of a substance in equilibrium with its liquid or solid phase at a given temperature.

2. How is vapor pressure of water calculated?

Vapor pressure of water can be calculated using the Antoine equation, which takes into account the temperature and properties of the specific substance. Alternatively, vapor pressure tables can also be used to determine the vapor pressure at a given temperature.

3. What factors affect the vapor pressure of water?

The vapor pressure of water is affected by temperature, atmospheric pressure, and the presence of other substances in the environment. Higher temperatures and lower atmospheric pressures generally lead to higher vapor pressures, while the presence of other substances can increase or decrease the vapor pressure depending on their interactions with water molecules.

4. Why is vapor pressure of water important?

Vapor pressure of water is important in various industrial and scientific processes, such as distillation and evaporation. It also plays a crucial role in weather phenomena, such as cloud formation and precipitation.

5. How does vapor pressure of water relate to humidity?

Vapor pressure of water is directly related to humidity. Higher vapor pressure means higher humidity, and vice versa. This is because humidity is a measure of the amount of water vapor present in the air, and vapor pressure is a measure of the tendency of water molecules to escape into the gas phase.

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