What will be the boiling point of $1 \ m$ urea solution in $K$ unit? $(K_b = 0.52 \ K \ kg \ mol^{-1})$

If an aqueous solution contains $9 \%$ and $1 \%$ $(w/w)$ of two non-volatile non-electrolytes $X$ (molecular weight $180$) and $Y$ (molecular weight $50$) respectively,the boiling point of the solution in ${ }^{\circ} C$ is approximately $(K_b = 0.52 \ K \ kg \ mol^{-1})$

Which of the following solutions exhibits the lowest value of boiling point elevation assuming complete dissociation?

$A$ solution containing $2.5 \times 10^{-3} \ kg$ of a solute dissolved in $75 \times 10^{-3} \ kg$ of water boils at $373.535 \ K$. The molar mass of the solute is $..... \ g \ mol^{-1}$. [nearest integer] (Given: $K_b(H_2O) = 0.52 \ K \ kg \ mol^{-1}$,boiling point of water $= 373.15 \ K$)

The elevation in boiling point of a solution containing $1.8 \ g$ of glucose in $100 \ g$ of solvent is $0.1 \ ^\circ C$. Find the molal elevation constant of the liquid.

Explain why on addition of $1 \ mol$ of $NaCl$ to $1 \ litre$ of water,the boiling point of water increases,while addition of $1 \ mol$ of methyl alcohol to one litre of water decreases its boiling point.