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?

If equal moles of water and urea are taken in a flask,what is the percentage by weight of urea?

The molar concentration of chloride ions in the resulting solution of $300 \ mL$ of $3.0 \ M$ $NaCl$ and $200 \ mL$ of $4.0 \ M$ $BaCl_{2}$ will be (in $M$)

$25.3 \ g$ of sodium carbonate,$Na_2CO_3$ is dissolved in enough water to make $250 \ mL$ of solution. If sodium carbonate dissociates completely,the molar concentration of sodium ions,$Na^{+}$,and carbonate ions,$CO_3^{2-}$,are respectively:
(Molar mass of $Na_2CO_3 = 106 \ g \ mol^{-1}$)

$250 \, mL$ of a sodium carbonate solution contains $2.65 \, g$ of $Na_2CO_3$. If $10 \, mL$ of this solution is diluted to $1 \, L$,what is the concentration of the resultant solution? (Molecular weight of $Na_2CO_3 = 106$)

Molality $(m)$ of $3 \text{ M}$ aqueous solution of $NaCl$ is:
(Given: Density of solution = $1.25 \text{ g mL}^{-1}$, Molar mass in $\text{g mol}^{-1}$: $Na = 23$, $Cl = 35.5$) (in $\text{m}$)