Which of the following is NOT a characteristic of Schottky defect?

Calculate the van't Hoff factor of a centimolar solution of potassium ferrocyanide if it is $60\%$ dissociated at $300$ K.

$5$ g urea is dissolved in $100$ g water. Find the amount of glucose to be dissolved in $120$ g of water so that the boiling points of both solutions will be the same.
[Molar mass of urea $= 60$ g $\text{mol}^{-1}$ & Molar mass of glucose $= 180$ g $\text{mol}^{-1}$]

Which of the following solutes has the ratio of theoretical molar mass to the experimentally observed molar mass is $3$?