What atmospheric pressure makes water boil at 20°C?

[ybhathena]

What does the atmospheric pressure have to be to make the boiling point of water 20 C?

 

[Feodalherren]

Google "Clausius-Clapeyron equation" and apply it...

 

[ybhathena]

Oh ok that seems to be what I need. Its a little bit advanced, could you explain the general idea of how to use this formula? I am a bit new

 

[Feodalherren]

Hmm... Well that would be a very involved answer. You should be able to handle it if you know basic algebra. I'm assuming you were given the values to plug in. Also it assumes that it's pure water. Impurities such as salt require the chemical process to first break the hydrogen bonds making water boil at a higher temperature.

I did it for you quickly and got an an answer of 18,900m rounded.

Edit: Actually that can't be correct. That's the limit where water boils at the internal temperature of a human, 37 C. I must have messed up my arithmetic.

 

[maimonides]

Wikipedia is your friend.
http://en.wikipedia.org/wiki/Steam_table#Water.2Fsteam_equilibrium_properties
(They give about 25 mbar)