Which from following mixtures in water acts as a basic buffer?

Which from following molecules does not have lone pair of electrons in valence shell of central atom?

Calculate the molar mass of non volatile solute when 1 g of it is dissolved in 100 g solvent decreases its freezing point by 0.2 K . $\left[\mathrm{K}_{\mathrm{f}}=1.2 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}\right]$

Which from following statements is NOT true about lyophilic colloids?