what is the easy way to calculate the osmotic pressure for electrolyte and non-electrolyte solutions?

Answer 1

Osmotic pressure for non-electrolytes is:

π=MRT

M is the concentration in mole/L
R=0.082 L*atm/(mole*K)
T the absolute temperature

For electrolytes

π=iMRT

where i is the Van't Hoff coefficient. For strong electrolytes it is equal to the total number of ions that comes from the 100% dissociation of one molecule of the electrolyte (e.g. for NaCl i=2, for Na2SO4 i=3, etc)

For weak electrolytes you have to consider the degree of dissociation and then it gets a bit more complicated.Then

i=(1-a)+na

where a is the degree of dissociation

n is the total number of ions that would come from the 100% dissociation of one molecule of the electrolyte.

For example let's assume we have CH3COOH and the a=80% (I made the value up)
Then n=2 since CH3COOH <=> CH3COO- + H+
and i=(1-0.8)+2*0.8= 0.2+1.6 =1.8

Answer 2

We need to know the molar concentration of dissolved species in order to calculate the osmotic pressure of an aqueous solution. We calculate the osmotic pressure, (pi), using the following equation:

Where:
M is the molar concentration of dissolved species (units of mol/L).
R is the ideal gas constant (0.08206 L atm mol-1 K-1, or other values depending on the pressure units).
T is the temperature on the Kelvin scale.

Answer 3

Wont PV=nRT do?

I believe it will. Practically a semi permeable membrane inside the container full of... and the level it rises in the tube neglecting edge effects....blah blah blah

Answer 4

I use a tire gauge.