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Solutions

Question
CBSEENCH12005713

How does osmotic pressure depend on molality of the solution?

Solution

Answer:
osmotic pressure is proportional to the molarity, C of the solution at a given temperature T. Thus: Π = C R T 
Here Π is the osmotic pressure and R is the gas constant. 
Π = (n2 /V) R T 
Here V is volume of a solution in litres containing n2 moles of solute. If w2 grams of solute, of molar mass, M2 is present in the solution, then n2 = w2 / Mand we can write,

 in a dilute aqueous solution molarity is equal to molality.
c = m when p = 1 and solution is dilute.
π = nB RTV = cRT = mRT

The osmotic pressure will increase with an increase in molality of the solution at a given temperature.