If the density of some lake water is $1.25\, g\, mL^{-1}$ and contains $92\, g$ of $Na^{+}$ ions per $kg$ of water,calculate the molality of $Na^{+}$ ions in the lake. (in $, m$)

If the concentration of glucose $(C_{6}H_{12}O_{6})$ in blood is $0.72 \ g \ L^{-1}$,the molarity of glucose in blood is $..... \times 10^{-3} \ M$. (Nearest integer)
(Given: Atomic mass of $C=12, H=1, O=16 \ u$)

The molarity of the solution obtained by mixing $750 \ mL$ of $0.5 \ (N) \ HCl$ with $250 \ mL$ of $2 \ (M) \ HCl$ is ........... $M$.

The molality of a $10\%\ (v/v)$ solution of di-bromine in $CCl_4$ (carbon tetrachloride) is $x$. $x = ...... \times 10^{-2}\ m$. (Nearest integer)
[Given : molar mass of $Br_2 = 160\ g\ mol^{-1}$
atomic mass of $C = 12\ g\ mol^{-1}$
atomic mass of $Cl = 35.5\ g\ mol^{-1}$
density of dibromine $= 3.2\ g\ cm^{-3}$
density of $CCl_4 = 1.6\ g\ cm^{-3}$]

$A$ solution is obtained by mixing $300 \, g$ of $25 \%$ solution and $400 \, g$ of $40 \%$ solution by mass. Calculate the mass percentage of the resulting solution. (in $\%$)

When $120 \ g$ of urea (molar mass $= 60 \ g/mol$) is dissolved in $1000 \ g$ of water,the density of the resulting solution is $1.15 \ g/mL$. The molarity of this solution is ........ $M$.