I need help on a chemistry problem PLEASEEE

1. Feb 24, 2006

jKotha

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? PLEASE HELP!! Thanks guys

Jkotha

2. Feb 25, 2006

biochemist

Is it something related to the equation for ideal gas? but in pV = nRT, the "n" has changed cos in 43.0 C water is liq but vapor is gas. Sorry, i've got no idea about it since I'm doing biology...

3. Feb 25, 2006

GCT

first things first, state the full problem.

4. Feb 25, 2006

jKotha

Full Problem

um.. that is the full problem. PV=NRT gives me the total pressure. I just need to find the vapor pressure of water.

This is what the problem says.
Consider the following data:
Temp = 43.0C Volume = 6.63ml
Barometric Pressure = 758.3 torr

a. Find the moles of air trapped in the cylinder

Ok, I can do this part by solving for n, in the ideal gas law. This is not a problem... the second part is the problem.

b. Calculate the vapor pressure of water, Pwater, at 43.0C

THIS IS THE FULL PROBLEM. Now I would really appreciate it if you can help. Thanks Guys..

jkotha

5. Feb 26, 2006

Plastic Photon

Assume that the total pressure is 760 torr and 758.3 as the partial pressure of the gas.

6. Feb 27, 2006

jKotha

Thanks.. that might help

would that mean that the vapor pressure of the water would be 1.7 torr? That seems incredibly low. I'm assuming that total pressure = Pressure(gas) + pressure(water)

760 = 758.3 + Pwater

.. this doesnt seem right. That is really low.

hm... I don't know why this is so tough.

thanks

jkotha

7. Feb 27, 2006

Plastic Photon

It is not that unusual, water is a liquid and so the particles are not moving around as much as they are in its gaseous state of steam.