FINDING WATER VAPOR PRESSUREEEEEeEEEEE?!?!?

Question

How do you find the water vapor pressure in mm Hg's from the temperature? I need the formula. PLEASE. !!

for example. if it were 12 degrees celsius, what would the water vapor pressure be? like that.

how would dalton's law help? that's just finding partial pressures of stuff. not the water vapor pressure.

Answer 1

For the most part, there is no formula but you need a TABLE of the vapor pressures of water at different temperatures. This table will show you the pressures, sometimes in different units, like mmHg, torr, pascals, etc. These tables are usually at the back of the book or any Handbook of Physical and Chemical Data.

If you just need an estimate, then think that the vapor pressure of water at its boiling point -- 100 C is 760 mm Hg. and approximate that vapor pressure is zero at 0 C, then by simple linear extrapolation you can say about 92 mmHg. Compare this with actual data from tables. By the way, the variation of the vapor pressure with temperature is more like a quadratic equation. Absent of that, the linear interpolation is your first educated guess.

You can use the "Lange's Handbook of Chemistry" or the "CRC Handbook"

Answer 2

Look in the back of your textbook. Or use Daltons Law of Partial Pressures.