The mole fraction of a solvent in an aqueous solution of a solute is $0.8$. The molality (in $mol \ kg^{-1}$) of the aqueous solution is:

$3.0 \ g$ ethanoic acid in $50 \ g$ benzene has . . . . . . molality. (Atomic weights: $H=1, C=12, O=16$).

$25 \ g$ of a solute of molar mass $250 \ g \ mol^{-1}$ is dissolved in $100 \ mL$ of water to obtain a solution whose density is $1.25 \ g \ mL^{-1}$. The molarity and molality of the solution are respectively

What mass of ethanol in $g$ must be added to $1.0 \, kg$ of water to have a mole fraction of ethanol equal to $0.2$?

Calculate the mole fraction of solute in the solution if the solution is prepared by dissolving $394 \ g$ of a nonvolatile solute in $622 \ g$ of water at $30^{\circ}C$ (Molar mass of solute $= 342 \ g \ mol^{-1}$).

The density of a solution prepared by dissolving $120 \ g$ of urea (mol. mass $= 60 \ u$) in $1000 \ g$ of water is $1.15 \ g/mL$. The molarity of this solution is : ............ $M$