What will be the mass percentage of an aqueous solution of $NaOH$ in which the mole fraction of $NaOH$ is $0.2$ (in $\% W/W$)?

The hardness of a water sample due to $MgSO_4$ is $50 \, ppm$. Calculate the amount of $MgSO_4$ in $mg$ present in $1 \, kg$ of water.

The density of a $1.0 \ M$ aqueous solution of glucose is $1.1 \ g/mL$. What is the molality of the solution in $m$ (in $m$)?

The mole fraction of ethanol in water is $0.08$. Its molality is

Calculate the mass percentage of aspirin $(C_{9}H_{8}O_{4})$ in acetonitrile $(CH_{3}CN)$ when $6.5 \ g$ of $C_{9}H_{8}O_{4}$ is dissolved in $450 \ g$ of $CH_{3}CN$.

What will be the molality of $10\%$ w/w aqueous solution of $NaOH$ (in $m$)? (Molecular mass of $NaOH = 40 \ g \ mol^{-1}$)