If w2 grams of solute, of molar mass, M2 is present in the solution, then
n2 = w2 / M2 and we can write,
P V =
2
2
 
 
 
w
MR T
(1 41)
or M2 =
∏
w2  
R T
V
(1 42)
Thus, knowing the quantities w2, T, P and V we can calculate the
molar mass of the solute Measurement of osmotic pressure provides another method of
determining molar masses of solutes