Identify rare earth element from following.

0.2 molal aqueous solution of KCl freezes at $-0.680^{\circ} \mathrm{C}$. Calculate van't Hoff factor for this solution. $\left(\mathrm{K}_{\mathrm{f}}=1.86 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}\right)$

0.1 molal aqueous solution of glucose boils at $100.16^{\circ} \mathrm{C}$. What is boiling point of 0.5 molal aqueous solution of glucose?

Identify a polymer obtained from $\beta$-hydroxybutyric acid and $\beta$-hydroxyvaleric acid.