$A$ solution is prepared by adding $2 \ g$ of a substance $A$ to $18 \ g$ of water. Calculate the mass per cent of the solute. (in $\%$)

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

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

$3.0$ molal $NaOH$ solution has a density of $1.110 \ g/mL$. The molarity of the solution is :-

Calculate the molarity $(M)$ of a $63 \% \ w/w$ $HNO_3$ solution if the density is $5.4 \ g/mL$.

Concentration terms such as mass percentage,$ppm$,mole fraction,and molality are independent of temperature,whereas molarity is a function of temperature. Explain.