0
$\begingroup$

I am a high school student and I am very confused in how we define osmotic pressure? Osmotic pressure is defined as the pressure required to stop the diffusion of solvent into a solution by applying external pressure over solution, which means that when the pure solvent is diffusing into the solution then it will apply pressure on the semi permeable membrane and when we have applied the same external pressure over the solution then there is no net movement of solvent occurs across the membrane and mathematically it is equal to P=cRT, where c is the concentration of solution , T is temperature in kelvin and R is the universal gas constant, if we go by this equation and calculate the osmotic pressure of 1 molar concentrated solution at room temperature it comes out to be almost 2495Pa which means 2495Newton/m^2 which is very high pressure and it doesn't seem to be true as osmosis is very slow process it surely cannot generate that much of pressure( just to imagine how large is that pressure assume an area of 1m^2 and place Mass of 249.5kg on it), so I think that it should not be that higher, so ,I am unable to understand what is actually osmotic pressure ,on which does it actually act and how do we actually calculate it?

we say that when a cell is placed in hypotonic solution then osmotic pressure is greater than Turgor pressure and water will flow inside the cell, but I have a confusion that :like turgor pressure acts on the wall/membrane of cell ,osmotic pressure(O.P)) should also act on the membrane and in opposite direction of turgor pressure, so by this logic wall should compress more as osmotic pressure on it will cause it to compress and turgor pressure will cause it to expand but Osmotic pressure is greater than turgor pressure(T.P) it should compress, but it doesn't happen? we only talk of turgor pressure(T.P) to explain the expansion but not osmotic pressure why? I know I am going wrong somewhere if Osmotic pressure would really leads the cell to compress then an animal cell would have never burst in hypotonic solution. and if osmotic pressure is also acting on the wall or membrane then net pressure on the wall is O.P-T.P (in inward direction) , and not only T.P (outward) so the wall pressure here also should not be same as turgor pressure? I think I should think of Osmotic pressure not as the pressure generated by the molecules hitting over the surface, but I should think of Osmotic pressure as the ability to take up water i.e I think we have just relate the concentration gradient in terms of actual pressure just to feel the things and to define them numerically to relate it with the actual pressure needed to stop the uptake of water.

If anyone will explain me this by giving as many examples as possible than it would be very helpful for me to understand because its my first time I came to know about these things.

$\endgroup$
3
  • $\begingroup$ 2495 Pa seems to quite low, equivalent to 0.0246 atm. $\endgroup$ – M. Farooq Jan 1 at 16:04
  • $\begingroup$ Please do respect ponctuation rules when writing. Thirteen lines in one sentence is nearly unreadable. $\endgroup$ – Maurice Jan 1 at 17:46
  • $\begingroup$ Some languages do not have punctuation marks, and when the brain does the conversion/translation work of run on thoughts, the result is like that. :-) $\endgroup$ – M. Farooq Jan 1 at 17:51

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.