If bond formation energy of $\mathrm{H}-\mathrm{H}$ bond is $-433 \mathrm{~kJ} \mathrm{~mol}^{-1}$ find the bond dissociation energy for 0.5 mole $H_{2(g)}$.

Identify homopolymer from following.

Which from following molecules has two lone pair of electrons in valence shell of its central atom?

Identify the product ' B ' in the following sequence of reactions. Propanone $\xrightarrow{\mathrm{B_a}(\mathrm{OH})_2} A \xrightarrow[-\mathrm{H}_2 \mathrm{O}]{\Delta} B$