$A$ $1$ molal solution is defined as $1$ mole of solute dissolved in:

If $50 \%$ of $1 \ M \ Na_2SO_4$ is dissociated in an aqueous solution of density $1.2 \ g \ mL^{-1}$,what is the molality of $Na^{+}$ ion in the solution?

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 ......... $M$.

State whether the following sentences are true $(T)$ or false $(F)$.
$(a)$ Concentration of pure water is $1.0 \ mol \ L^{-1}$.
$(b)$ Concentration of pure water is $55.5 \ mol \ L^{-1}$.

Calculate the mass of urea $[NH_2CONH_2]$ required in making $2.5 \ kg$ of $0.25 \ m$ aqueous solution. (in $g$)

$3.0\, g$ of oxalic acid $[(CO_2H)_2 \cdot 2H_2O]$ is dissolved in a solvent to prepare a $250\, mL$ solution. The density of the solution is $1.9\, g/mL$. The molality and normality of the solution,respectively,are closest to