Which from following ionic crystals exhibits Frenkel defect?

An aqueous solution has an osmotic pressure of $4.92$ atm at $300$ K.
Calculate the molarity of the solution.
($R = 0.082$ L atm mol$^{-1}$ K$^{-1}$)

A solution is prepared by dissolving $68$ g sucrose in $1$ kg water. Calculate the vapour pressure of solution at $298$ K. [vapour pressure of water at $298$ K = $18$ mm of Hg & mole fraction of solvent = $0.9964$]

Which of the following statements is NOT true about solubility?