Sup /sci/. I have learned two things about osmosis across semipermeable

>>8008818
Both happen at the same time and eventually reach an equilibrium.

Oh hey you're that anon that tested his π latex in that one thread from earlier.

>>8008818
To further expound on this: If you consider the osmotic pressures of the two solutions in the pipe on the left in my OP picture, you can see that solution P1a has more solutes than solution P2a, and thus P1a has a higher osmotic pressure than P2a, which dictates that water will flow from P1a to P2a.

This clearly does not happen, as evident by the tube on the right-hand side, where the opposite has happened.

>>8008840
Yeah, around 10 minutes before I made this thread. Just wanted to make sure I didn't mess up the math tags.

>>8008839
I would appreciate it if you read my question before attempting to answer it.

>>8008850
Alright I'll elaborate

Osmotic Π pressure resists water flowing in.
Concentration difference ΔC draws water in.

Depending on starting conditions eventually Π=ΔC and water flow ceases.

>>8008859
Now I can see what you mean, and although it makes sense to me, I'm still not completely satisfied.

From wikipedia:
>The phenomenon of osmosis arises from the propensity of a pure solvent to move through a semi-permeable membrane and into a solution containing a solute to which the membrane is impermeable.

Disregarding the very odd wording ("to which the membrane is impermeable"), this statement is equivalent to saying that water will move to the solution with the higher solute concentration.

Now, how can an increased resistance to inward osmosis cause more inward osmosis? Wouldn't that literally be a decreased resistance to inward osmosis?

In addition, is it not possible to predict equilibrium concentrations if you have two solutions with known solute concentrations?

Shameless self-bump. I still don't think I've got an adequate answer to this.

you've fallen victim to poor terminology

>>Osmotic pressure is the minimum pressure which needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane.
as you've written, it means the pressure an outside observer needs to apply to that half of the system to prevent movement of water. That is, it's the pressure a human would need to apply to P1a in your diagram to prevent the movement of water from P2a

adding solute to a solution increases the osmotic potential and causes the movement of water, and if you want to fight it, you need to apply a pressure equal to that potential

http://chemwiki.ucdavis.edu/Textbook_Maps/General_Chemistry_Textbook_Maps/Map%3A_Chem1_%28Lower%29/08._Solution_Chemistry/8.4%3A_Osmosis_and_Osmotic_Pressure
>One way to stop osmosis is to raise the hydrostatic pressure on the solution side of the membrane. This pressure squeezes the solvent molecules closer together, raising their escaping tendency from the phase. If we apply enough pressure (or let the pressure build up by osmotic flow of liquid into an enclosed region), the escaping tendency of solvent molecules from the solution will eventually rise to that of the molecules in the pure solvent, and osmotic flow will case. The pressure required to achieve osmotic equilibrium is known as the osmotic pressure. Note that the osmotic pressure is the pressure required to stop osmosis, not to sustain it.
>Osmotic pressure is the pressure required to stop osmotic flow It is common usage to say that a solution “has” an osmotic pressure of "x atmospheres". It is important to understand that this means nothing more than that a pressure of this value must be applied to the solution to prevent flow of pure solvent into this solution through a semipermeable membrane separating the two liquids.

>>8008985
>you've fallen victim to poor terminology

Would you please expound on this statement? I had some vague intuition that this was the case, but I still can't put words to it.

>One way to stop osmosis is to raise the hydrostatic pressure on the solution side of the membrane. This pressure squeezes the solvent molecules closer together, raising their escaping tendency from the phase.

Does this apply to water as a solvent as well? I ask because I've been taught that water is incompressible.

From the above greentext:

>This pressure squeezes the solvent molecules closer together, raising their escaping tendency from the phase.

I assume this is directly related to Brownian motion?

Now, call me a retard because I probably am, but it seems I need the answer to the following question spoonfed to me:

>Now, how can an increased resistance to inward osmosis cause more inward osmosis? Wouldn't that literally be a decreased resistance to inward osmosis?

>>8009012
Oh wait, I think I just got it. Please respond to this post if you are so inclined.

Osmotic pressure isn't a measure of a solution's resistance to inward osmosis, it is the hypothetical pressure you would have to apply to a solution to prevent inward osmosis. If you add more solute to one solution, the hypothetical pressure you would need to add to this solution to prevent inward osmosis would obviously increase due to increased concentration gradients.

I would very much like a comment on the above paragraph. I would also like to ask if I'm completely retarded, because I've used a lot of different sources on this, and they all worded it the same. It just seems it could be worded in a much better way to avoid this misunderstanding.

>>8009022
Just read the wiki. Think you may be retarded.
Higher osmotic pressure implies greater solute movement in

>>8009022
you have it correct

>>8008818
Get a stat-mech book and read about chemical potential. That will tell you the physics of osmosis. Chemical potential is like a temperature, but instead of giving you the flow of heat - it gives you the flow of particles.