At the freezing point of a solution containing a nonvolatile solute,which of the following are in equilibrium?

Which of the following solutions will have the lowest freezing point?

$A$ solvent freezes at $17^{\circ} C$ and it has a latent heat of fusion of $180 \ J \ g^{-1}$. The molal depression constant $(K_{f})$ of the solvent is (in $K \ kg \ mol^{-1}$):

Which of the following has the lowest freezing point?

$A$ solution containing $7.5 \ g$ of urea (molar mass $= 60 \ g \ mol^{-1}$) in $1 \ kg$ of water freezes at the same temperature as another solution containing $15 \ g$ of solute $X$,in the same amount of water. The molar mass of $X \ (g \ mol^{-1})$ is

What is the molality of a solution that has a freezing point depression of $3 \ K$ and a freezing point depression constant of $5 \ K \ kg \ mol^{-1}$ (in $m$)?