What is the molality of a solution containing $300 \ mg$ of urea (molar mass $60 \ g/mol$) dissolved in $30 \ g$ of water (in $m$)?

The density of a $2.05 \ M$ solution of acetic acid $(CH_3COOH)$ in water is $1.02 \ g \ mL^{-1}$. The molality of the solution is ......... $mol \ kg^{-1}$.

What will be the molarity of a solution containing $5 \ g$ of sodium hydroxide in $250 \ mL$ solution?

Density of $3 \ M$ $NaCl$ solution is $1.25 \ g/mL$. The molality of the solution is : (in $m$)

$A$ sample of drinking water is severely contaminated with chloroform $(CHCl_3)$. $CHCl_3$ is considered carcinogenic in nature. The level of contamination was $15 \ ppm$ (by mass).
$(i)$ Express this in percent by mass.
$(ii)$ Determine the molality of chloroform in the water sample.

$25.3 \ g$ 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 $Na_2CO_3 = 106 \ g \ mol^{-1}$)