Question

At 25°c the highest osmotic pressure will be exhibited by

Answer 1

pie ( osmotic pressure ) = iMRT 

i = van't hoff factor 
M = concentration of solution [ in moles/litre OR molar ] 
R = universal gas constant 
T = temperature 

so, pie is directly proportional to i ( van't hoff factor ) 
so, more is the van't hoff factor, more will be it's osmotic pressure 

now remember it always that non-ionic organic compounds [ HERE GLUCOSE AND UREA BOTH ] have van't hoff factor of 1, 

and i for Cacl2 = 3; 
and i for KCl = 2; 

so, greatest i is with CaCl2, it's osmotic pressure is greatest 

REMEMBER COMPARISON OF THIS TYPE ONLY COMES WHEN TEMP., PRESSURE AND CONCENTRATIONS ARE SAME