An ionic compound is formed by elements X and Y. Element Y forms a face-centered cubic (FCC) lattice, and element X occupies one-third of the tetrahedral voids. What is the formula of the compound?

A metal crystallizes to form simple cubic unit cell. Calculate the void volume of unit cell. [$a = 3.36 \times 10^{-8}$ cm]

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$^{-1}$)