Write the formula for percentage by weight.

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

What type of solution is sea water?

If $5.85 \ g$ of $NaCl$ is dissolved in $90 \ g$ of water,then find out the mole fraction of $NaCl$.

$A$ compound $H_2X$ with molar weight of $80 \ g \ mol^{-1}$ is dissolved in a solvent having density of $0.4 \ g \ mL^{-1}$. Assuming no change in volume upon dissolution,the molality of a $3.2 \ M$ solution is:

If a solution is $98\% \ H_2SO_4$ by weight and has a density of $1.8 \ g/mL$,its molarity is ....... $M$.