Pure water freezes at $273 \mathrm{K}$ and $1 \mathrm{bar}$ pressure. The addition of $34.5 \mathrm{g}$ of ethanol to $500 \mathrm{g}$ of water changes the freezing point of the solution. Use the freezing point depression constant of water as $2 \mathrm{K} \mathrm{kg} {\mathrm{mol}}^{-1}$. The figures shown below represent the plots of vapour pressure ($\mathrm{V}.\mathrm{P}.$) versus temperature ($\mathrm{T}$). [Molecular weight of ethanol is 46 g $46 \mathrm{g} {\mathrm{mol}}^{-1}$]

Among the following, the option representing a change in the freezing point is

On dissolving $0.5\mathrm{ }\mathrm{g}$ of a non-volatile non-ionic solute to $39\mathrm{ }\mathrm{g}$ of benzene, its vapor pressure decreases from $650\mathrm{ }\mathrm{m}\mathrm{m}\mathrm{ }\mathrm{H}\mathrm{g}$ to $640\mathrm{ }\mathrm{m}\mathrm{m}\mathrm{ }\mathrm{H}\mathrm{g}.$ The depression of freezing point of benzene (in $\mathrm{K}$ ) upon addition of the solute is _______

(Given data: Molar mass and the molal freezing point depression constant of benzene are $78\mathrm{ }\mathrm{g}\mathrm{ }\mathrm{m}\mathrm{o}{\mathrm{l}}^{-1}$ and $5.12\mathrm{ }\mathrm{K}\mathrm{ }\mathrm{k}\mathrm{g}\mathrm{ }\mathrm{m}\mathrm{o}{\mathrm{l}}^{-1},$ respectively)

Give your answer up to three significant figures.

The plot given below shows $\mathrm{P}-\mathrm{T}$ curves (where, $\mathrm{P}$ is the pressure and $\mathrm{T}$ is the temperature) for two solvents $\mathrm{X}$ and $\mathrm{Y}$ and isomolal solutions of $\mathrm{NaCl}$ in these solvents. $\mathrm{NaCl}$ completely dissociates in both the solvents.



On the addition of equal number of moles of a non-volatile solute $\mathrm{S}$ in equal amount (in $\mathrm{kg}$) of these solvents, the elevation of boiling point of solvent $\mathrm{X}$ is three times that of solvent $\mathrm{Y}$. The solute $\mathrm{S}$ is known to undergo dimerization in these solvents. If the degree of dimerization is $0.7$ in the solvent $\mathrm{Y}$, the degree of dimerization in the solvent $\mathrm{X}$ is _______.