Question

When does the measurement of the olligative property of a soulution lead to abnormal molar mass

Answer 1

this is because of the ionisation of compound.

suppose, urea is in water it will not dissociate so observed mass will be equal to theoretical mass.

but is it is compound like HCl, NaCl, etc they show dissociation so observed mass will be different because each HCl molecule dissociate into 2 ions. so vann't hoff factor is there(i) = Normal mass/observed mass.

hope it would be enough