What is the mass ratio of ethylene glycol (${\mathrm{C}}_2{\mathrm{H}}_6{\mathrm{O}}_2$, molar mass $=62 \mathrm{g}/\mathrm{mol}$) required for making $500 \mathrm{g}$ of $0.25$ molal aqueous solution and $250 \mathrm{mL}$ of $0.25$ molar aqueous solution?

The volume of $\mathrm{HCl}$, containing $73\mathrm{g} {\mathrm{L}}^{-1}$, required to completely neutralise $\mathrm{NaOH}$ obtained by reacting $0.69 \mathrm{g}$ of metallic sodium with water, is _____ $\mathrm{mL}$. (Nearest Integer)

(Given : molar Masses of $\mathrm{Na},\mathrm{Cl},\mathrm{O},\mathrm{H}$ are $23,35.5,16$ and $1\mathrm{g} {\mathrm{mol}}^{-1}$ respectively)

Some amount of dichloromethane $\left({\mathrm{CH}}_2{\mathrm{Cl}}_2\right)$ is added to $671.141\mathrm{mL}$ of chloroform $\left({\mathrm{CHCl}}_3\right)$ to prepare $2.6\times {10}^{-3}\mathrm{M}$ solution of ${\mathrm{CH}}_2{\mathrm{Cl}}_2\left(\mathrm{DCM}\right)$. The concentration of $\mathrm{DCM}$ is _____ ppm (by mass).

Given: Atomic mass : $\mathrm{C}=12;\mathrm{H}:1;\mathrm{Cl}=35.5$ density of ${\mathrm{CHCl}}_3=1.49\mathrm{g} {\mathrm{cm}}^{-3}$

Assume carbon burns according to following equation :
$2\mathrm{C}\left(\mathrm{s}\right)+{\mathrm{O}}_2( \mathrm{g})\to 2\mathrm{CO}\text{ (s) }$
when $12 \mathrm{g}$ carbon is burnt in $48 \mathrm{g}$ of oxygen, the volume of carbon monoxide produced is $\_\_\_\_\_\_\times {10}^{-1} \mathrm{L}$ at STP [nearest integer]

[Given : Assume $\mathrm{CO}$ as ideal gas, Mass of $\mathrm{C}$ is $12 \mathrm{g} {\mathrm{mol}}^{-1}$, mass of $O$ is $16 \mathrm{g} {\mathrm{mol}}^{-1}$ and molar volume of an idal gas at STP is $22.7 \mathrm{L} {\mathrm{mol}}^{-1}$ ]

The density of $3\mathrm{M}$ solution of $\mathrm{NaCl}$ is $1.0 \mathrm{g} {\mathrm{mL}}^{-1}$. Molality of the solution is $\_\_\_\_\_\_\times {10}^{-2} \mathrm{m}$ (Nearest integer).

Given: Molar mass of $\mathrm{Na}$ and $\mathrm{Cl}$ is $23$ and $35.5 \mathrm{g}$ ${\mathrm{mol}}^{-1}$ respectively.