I was wondering how one would actually calculate how much oxygen would dissolve into water given the necessary initial conditions, and what those initial conditions would need to be. I assume they would be pressure, and initial concentration, but I really don't know where I would go from there. Clearly air and water have different concentrations of gases and liquids, despite having been in contact for thousands of years. And once in water, is oxygen still considered gaseous? I assume it is, but why is it called gaseous-what quality of it deems it a gas despite being surrounded by liquid?
[Physics] Dissolving oxygen into water
equilibriumphysical-chemistrythermodynamicswater
Related Solutions
Yes, it's possible though usually complicated.
If you have a sphere of water at 0ºC and put it in a freezer at some temperature T that is below zero then the rate of heat flow out from the sphere would be approximately given by Newton's law of cooling. If the cooling rate is slow, and you can make the approximation that the temperature within the water is constant then the heat flow per unit area will be constant while the water is freezing. The time to freeze would be the total latent heat of fusion divided by the heat flow rate per unit area divided by the total surface area.
However even in this simplified situation we don't know the constant of proportionality in Newton's law, and this will depend on the details of the environment e.g. speed of air currents. The best we could do is make conclusions like the freezing time will be proportional to the sphere radius because it's proportional to volume divided by area. We should also find the time is inversely proportional to the temperature difference.
Life gets more complicated when the cooling rate is too fast for us to assume no temperature gradient within the water. For example a skin of ice would form on the outside, and ice is a better insulator than water (because you get convection currents in water). In that case the rate of heat flow (and therefore freezing) would be inversely proportional to the thickness of the skin of ice.
A last complication is that water readily supercools. You can only assume the water will freeze at eactly 0ºC if there's no barrier to nucleation of ice crystals.
The melting point of nitrogen is greater than that of oxygen. Is gaseous oxygen really liquid oxygen dissolved in gaseous nitrogen? No. It is gaseous oxygen.
"Water vapour in the air" (your phrase) is just that - vapour. Not liquid droplets "dissolved" in air.
You may be confused by the fact that wet steam does contain water droplets, and the steam from a kettle is wet. However, it is perfectly possible to produce dry steam, and this stuff is enormously dangerous when let loose - it's invisible but will cook flesh almost instantly.
Your biggest mistake is to assume that evaporation is equivalent to a solid being dissolved, specifically salt into water. The difference can be illustrated by the fact that water will evaporate into any gas (with the obvious caveat that it must not react with the gas), and the rate is controlled by temperature and the partial pressure of water vapor in the surrounding atmosphere. Salt, on the other hand, simply will not dissolve in gasoline, and in fact will not dissolve in any non-polar liquid.
Best Answer
Air is a mixture of gases, and the concentration of oxygen dissolved in solution (in the water) is proportional to the partial pressure of oxygen in the air. Raoult's law states: The vapour pressure of an ideal solution is directly dependent on the vapour pressure of each chemical component and the mole fraction of the component present in the solution.