What is meant by mass percentage $( \% w/w )$?

The molarity of the solution prepared by dissolving $6.3 \ g$ of oxalic acid $(H_{2}C_{2}O_{4} \cdot 2H_{2}O)$ in $250 \ mL$ of water in $mol \ L^{-1}$ is $x \times 10^{-2}$. The value of $x$ is ..... . (Nearest integer)
[Atomic mass : $H: 1.0, C: 12.0, O: 16.0]$

The molarity of a solution of $Na_2CO_3$ having $10.6 \ g$ in $500 \ mL$ of solution is ......... $M$.

How many grams of $KCl$ would have to be dissolved in $60 \ g$ of $H_2O$ to give a $20 \%$ by weight solution?

The molality (in $mol \ kg^{-1}$) of $1 \ mol$ of solute in $50 \ g$ of solvent is

Which of the following modes of expressing concentration is independent of temperature?