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?

Calculate the percent dissociation of 0.02 m solution if its freezing point depression is 0.046 K .

$\left[\mathrm{K}_{\mathrm{f}}\right.$ for water $\left.=1.86 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1} ; \mathrm{n}=2\right]$