For different concentrations of aqueous solution of the semipermeable membrane on both sides, the minimum additional pressure in order to prevent water from low concentration to high concentration and side side penetration in high concentration is called osmotic pressure applied to one side. The osmotic pressure and the solution is not Semipermeable membrane
The number and the environment temperature.
osmotic pressure Definition
It can prevent additional pressure applied to the penetration occurs above the solution level is called Osmotic pressure
(the osmotic pressure)
osmotic pressure influence factor
Germany in 1877 Botanist
Fyfiel (Pfeffer) according to the experimental data found two rules:
(1) at a certain temperature, the concentration of osmotic pressure and solution of dilute solution is proportional to the
(2) in a certain concentration, osmotic pressure and dilute solution Thermodynamic temperature
Holland in 1886 Theoretical Chemistry
home vant hoff
(van't Hoff) is derived from the relationship between osmotic pressure and non volatile concentration and thermodynamic temperature for dilute electrolyte solutions:
The type known as fan, formula, also called osmotic pressure formula.
C is the mole concentration, unit: mol/L, can also be counted as C=n/V (molar volume (mol) / (L)).
R ideal gas
When the constant PI unit Pa, V unit of L (L), R = 8.314J - K-1 - mol-1.
T heat unit: K (Kelvin), and the conversion between Celsius is T (K) = 273+T (C), with 25 degrees Celsius =298 Kelvin.
Vantov formula, at a certain temperature, osmotic pressure and volume in the solution containing not by Semipermeable membrane
The number (the number of molecules or ions is proportional to the number), irrespective of the nature of solute.
osmotic pressure The osmotic pressure of the solution
osmotic pressure explain
The osmotic pressure of the solution simply refers to the solution Solute particles
Attraction to water. The osmotic pressure of the solution size depends on the number of unit volume of solute particles in solution: solute particle is more, the higher the concentration of water, the more attraction, the osmotic pressure of the solution is higher; in turn, solute particle less, the solution concentration is low, attraction to water is weaker, the osmotic pressure of the solution is low. With inorganic salt, protein content. In all kinds of inorganic salt ions in the extracellular fluid, has the advantage of the content is Na+ and Cl-, the osmotic pressure of extracellular fluid more than 90% from Na+ and Cl-. At 37 DEG C, the plasma osmotic pressure is about 770kPa, equivalent to the penetration of intracellular fluid pressure.
osmotic pressure Colligative properties
Because of the balance of osmotic pressure to follow the ideal Gas law
(ignoring the interaction between solute molecules in dilute solution), the mathematical derivation omitted here, finally come Vant Hoff
The relationship between =cRT (or: Pi Pi =kTN/V; N/V molecular number density), from the osmotic pressure of solution formula is determined by the number of molecules and the solute, osmotic pressure is colligative properties. This is not the real pressure, but to prevent the seepage pressure flow may be required, namely the system to achieve the required balance pressure difference.
osmotic pressure Cell associated
Plant cells to penetrate the water, its power is osmotic pressure. Then the osmotic pressure on cells of the world what is the significance? We must also take concrete data to illustrate, assume that the cell radius of R, due to osmotic pressure expansion into R+dR, so the increase in the area of PI was dA=8 RdR, the energy consumption for sigma x dA. If we want to let the cell expansion to achieve balance, is to make free energy
PdV is equal to Surface tension
, calculated by Laplasse formula: =Rp/2. If the red blood cell in pure water, the pressure of water is prevented from entering the cell 300pa, assuming cell diameter of 10 m, the cells are there? We estimate P Sigma =10 5m * 300pa/2=1.5 * 10 3Nm 1. This force is enough to tear Eukaryotic cells
That will destroy the cell. So you can't use pure water to dilute the red blood cells, so that they will burst, instant cell.
osmotic pressure Hydrophobic interaction
Emptying effect is a hydrophobic interaction (hydrophobic force is mixed entropy and free energy) ideal, and osmotic pressure is causing large molecules produced this emptying force. Osmotic pressure can be seen as per unit volume of free energy change. Emptying effect is small particles can get large particles pushed together, so that the small particles of their maximum entropy, if two surface matched accurately, the corresponding unit contact area on the free energy reduction for F/A=ckBT * 2R, R for the small particle radius (where the C concentration is not molecular number density).
Small particles can help large molecules effectively find each other specific recognition sites, commonly used in biological experiments, serum protein (BSA) and polyethylene glycol (PEG) as small particles, they are called blocking reagents. For example, they can help the deoxygenated hemoglobin and other protein together, solubility is reduced 10 times; dextran or PEG can stabilize the complex thermal decomposition, solubility of DNA can be increased; PEG and BSA can make the motor protein silk self-assembly rate or different enzyme activity increased by several orders of magnitude; in Escherichia coli DNA Replication system
If you do not join the blocking reagent will not work. The choice of blocking reagents is not important, the key is the scale and density of his relative molecular assembly. This is the ordered assembly while driving state of disorder in the process of the order is to smaller particles more disordered at the expense of.
osmotic pressure Relevant person Vant Hoff
Because of pressure and chemical kinetics of penetration won the first session Nobel Prize in Chemistry