Chemistry Forums for Students > Physical Chemistry Forum

How does Ammonia achieve -70°C in atmospheric pressure?

(1/3) > >>

R717NOVAH:
I can witness liquid NH3 achieving sub 'boiling point' temperatures by simpling removing a thermocouple from a container of liquid, typically around -40 to -60°C.

I see that as the Ammonia evaporates energy is lost from the liquid droplets and I would imagine a loss in density.

With the exception of mathematical explanations from the works of Geoffrey D. Kaiser & Richard F. Griffiths, I am yet to find an explanation that hits home of how this occurs other than terms like entrained air and adiabatic volumetric expansion, partial pressures etc. I would like to find some visualisation of what is exactly going on in this process.

AWK:
Look at the ammonia phase diagram.

R717NOVAH:

--- Quote from: AWK on September 13, 2020, 05:55:40 AM ---Look at the ammonia phase diagram.

--- End quote ---
The P/T of Ammonia at equilibrium indicates - 33°C am I missing something, how does it drop below this point without a drop in pressure?

AWK:
You have to cool the ammonia - otherwise, the temperature will not drop. At a pressure of 1 Atm. liquid ammonia exists in the temperature range of ~-75 to -33°C.

R717NOVAH:
 
--- Quote from: AWK on September 13, 2020, 03:10:29 PM ---You have to cool the ammonia - otherwise, the temperature will not drop. At a pressure of 1 Atm. liquid ammonia exists in the temperature range of ~-75 to -33°C.

--- End quote ---
This is the object of my question - how is the Ammonia being cooled below -33°C ?

Navigation

[0] Message Index

[#] Next page