Calculate van't Hoff factor of aqueous solution of 0.18 m electrolyte that freezes at $-0.54^{\circ} \mathrm{C}$.

$\left(\mathrm{K}_{\mathrm{f}}\right.$ for solvent $\left.=1.86 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}\right)$

What is the molar mass of third homologue of alkane series?

Which from following polymers is used to obtain oil seals?

Which element from following has largest ionic size in +3 state?