Identify the substrate ' A ' in the following conversion.

$$A \xrightarrow[\mathrm{H}_3 \mathrm{O}^{+}]{\mathrm{AlH}(\mathrm{~i-Bu})_2} \text { Pent-3-enal }$$

Find the number of moles of sodium atoms in $6.9 \times 10^{-2} \mathrm{~kg}\left(\right.$ Atomic mass $\left.=23 \mathrm{~g} \mathrm{~mol}^{-1}\right)$

Identify the product ' B ' in the following sequence of recations.

$$\mathrm{CH}_3 \mathrm{Br} \xrightarrow{\mathrm{KCN}} \mathrm{~A} \xrightarrow{\mathrm{Na}_2 / \mathrm{C}_2 \mathrm{H}_5 \mathrm{OH}} \mathrm{~B}$$

Which of the following elements belongs to second group and fifth period of periodic table?