The number of moles of solute per $kg$ of a solvent is called its

$A$ solution is prepared by dissolving $24.5 \ g$ of sodium hydroxide in distilled water to give $1 \ L$ solution. The molarity of $NaOH$ in the solution is (Given that molar mass of $NaOH = 40.0 \ g \ mol^{-1}$) (in $M$)

The solutions $A$ and $B$ are $0.1 \ M$ and $0.2 \ M$ in a substance. If $100 \ mL$ of $A$ are mixed with $25 \ mL$ of $B$ and there is no change in volume,then the final molarity of the solution is ......... $M$.

If the mole fraction of a solute in liquid naphthalene $(C_{10}H_8)$ is $0.2$,then the molality of the solution will be .............. $m$.

Molality of $30 \% \ w/w$ aqueous solution of $NaOH$ is . . . . . . . (in $m$)

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.