$$ \text {During estimation of nitrogen by Dumas' method of compound } \mathrm{X}(0.42 \mathrm{~g}) $$

_________mL of $\mathrm{N}_2$ gas will be liberated at STP. (nearest integer)

Consider the following reactions

$$ \begin{aligned} & \mathrm{A}+\underset{\substack{ \text { Little } \\ \text { amount }}}{\mathrm{NaCl}}+\mathrm{H}_2 \mathrm{SO}_4 \rightarrow \mathrm{CrO}_2 \mathrm{Cl}_2+\text { Side Products } \\ & \mathrm{CrO}_2 \mathrm{Cl}_{2 \text { (Vapour) }}+\mathrm{NaOH} \rightarrow \mathrm{~B}+\mathrm{NaCl}+\mathrm{H}_2 \mathrm{O} \\ & \mathrm{~B}+\mathrm{H}^{+} \rightarrow \mathrm{C}+\mathrm{H}_2 \mathrm{O} \end{aligned} $$

The number of terminal ' $O$ ' present in the compound ' C ' is__________

0.5 g of an organic compound on combustion gave 1.46 g of $\mathrm{CO}_2$ and 0.9 g of $\mathrm{H}_2 \mathrm{O}$. The percentage of carbon in the compound is _______________. (Nearest integer)

[Given : Molar mass (in $\left.\mathrm{g} \mathrm{mol}^{-1}\right) \mathrm{C}: 12, \mathrm{H}: 1, \mathrm{O}: 16$ ]

The number of optical isomers exhibited by the iron complex $(\mathrm{A})$ obtained from the following reaction is___________.

$$ \mathrm{FeCl}_3+\mathrm{KOH}+\mathrm{H}_2 \mathrm{C}_2 \mathrm{O}_4 \rightarrow \mathrm{~A} $$