In ionic solid, anions are arranged in ccp array and cations occupy $1 / 3$ tetrahedral voids. What is the formula of ionic compound?

[Consider $\mathrm{A}=$ cation; $\mathrm{B}=$ anion]

Which of the following is NOT dihydric phenol?

Calculate the concentration of an aqueous solution of non electrolyte at 300 K if its osmotic pressure is 12 atm .

$$ \left[\mathrm{R}=0.0821 \mathrm{~atm} \mathrm{dm}^3 \mathrm{~K}^{-1} \mathrm{~mol}^{-1}\right] $$

Which from following compounds is least soluble in water at STP?