First, I'll go ahead and say I'm not very versed in chemistry. My question comes from my interest in planetary-sciences, specifically the speculation that there are likely exoplanets and moons with surface oceans of water-ammonia. However I can't find much hard info on how a vast body (i.e. ocean) of water-ammonia would behave differently than just water.
In short my question is how might a water-ammonia ocean differ from a "pure" water ocean in terms of:
- Ice(s) formation
- Changes in water/ammonia ratio based on the above two factors (ice formation and evaporation).
This seems largely like a chemistry question to me. If I'm wrong please let me know which Stack Exchange you think I should post in. :)
- 5% - 40% ammonia.
- Temperature range: -80C to 15C
- Atmospheric Pressure: 0.5 bar to 30 bar.
I've heard that the freezing and boiling points of the mixed liquid would exist on some continuum between the freezing and boiling points of its constituent liquids (ammonia and water), varying depending on the exact mix ratio and of course pressure. Is that correct?
What I'd like to most wrap my head around is whether the water-ammonia mix would behave as a single uniform liquid, freezing and evaporating at a rate determined by the average of the mix's freezing/boiling point, or whether the ammonia molecules would start to evaporate before the water molecules, and the water molecules start to form ice before the ammonia molecules.
If the later behavior is correct I could imagine an ocean of water-ammonia varying substantially in its water/ammonia ratio from pole to equator thanks to the greater heat near the equator and the ammonia molecules evaporating.