$200 \ g$ of $20 \% \text{ } w/w$ urea solution is mixed with $400 \ g$ of $40 \% \text{ } w/w$ urea solution. What is the weight percentage $(w/w \%)$ of the resultant solution (in $.33$)?

The concentration of $Ca^{2+}$ ions in a water sample is $0.0002 \ M$. What is the concentration of $Ca^{2+}$ in $ppm$ by weight-volume?

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 : $H: 1.0, C: 12.0, O: 16.0]$

$A$ solution of sugar is obtained by mixing $200 \ g$ of its $25 \%$ solution and $500 \ g$ of its $40 \%$ solution (both by mass). The mass percentage of the resulting sugar solution is $..........$. (Nearest integer)

If $25 \ mL$ of $0.25 \ M$ $NaCl$ solution is diluted with water to a volume of $500 \ mL$,the new concentration of the solution is (in $M$)

What is the mass of glucose in $500 \ g$ of an aqueous solution of glucose with a molality of $0.5 \ m$?