The molarity of the solution prepared by dissolving $6.3 \mathrm{g}$ of oxalic acid $\left({\mathrm{H}}_2{\mathrm{C}}_2{\mathrm{O}}_4·2{\mathrm{H}}_2\mathrm{O}\right)$ in $250 \mathrm{mL}$ of water in $\mathrm{mol} {\mathrm{L}}^{-1}$ is $\mathrm{x}\times {10}^{-2}.$ The value of $\mathrm{x}$ is _________ . (Nearest integer)
[Atomic mass : $\mathrm{H} : 1.0, \mathrm{C} : 12.0, 0 : 16.0 \mathrm{J}$]

Henry's constant (in kbar) for four gases $\mathrm{\alpha },\mathrm{\beta },\mathrm{\gamma }$  and $\delta$ in water at $298 \mathrm{K}$ is given below :

$\begin{array}{ccccc}& \mathrm{\alpha }& \mathrm{\beta }& \mathrm{\gamma }& \mathrm{\delta }\\ {\mathrm{K}}_{\mathrm{H}}& 50& 2& 2\times {10}^{-5}& 0.5\end{array}$

(density of water $={10}^3 \mathrm{k} {\mathrm{gm}}^{-3}$ at $298 \mathrm{K}$ ) This table implies that :

The freezing point of benzene decreases by ${0.45}^{°}\mathrm{C}$ on adding $0.2\mathrm{ }\mathrm{g}$ of acetic acid to $20 \mathrm{g}$ of benzene. If acetic acid associates to form a dimer in benzene, then what is the percentage association of acetic acid in benzene?

$\left({\mathrm{K}}_{\mathrm{f}} \mathrm{for}\mathrm{ }\mathrm{benzene}=5.12\mathrm{ }\mathrm{K}\mathrm{ }\mathrm{kg}\mathrm{ }{\mathrm{mol}}^{-1}\mathrm{ }\right)$