If the mole fraction of water in a solution of $H_2SO_4$ is $0.85$,then the molality of the solution is:

The sum of the mole fraction of the components of a solution is

$10.30 \; mg$ of $O_2$ is dissolved in $1 \; L$ of seawater with a density of $1.03 \; g/mL$. The concentration of $O_2$ in $ppm$ is:

The density of a nitric acid solution is $1.5 \ g \ mL^{-1}$. Its weight percentage is $68 \%$. What is the approximate concentration (in $mol \ L^{-1}$) of nitric acid? $(N=14 \ u, O=16 \ u, H=1 \ u)$

Molar concentration $(M)$ of any solution $=$

$50 \ g$ of a substance is dissolved in $1 \ kg$ of water at $90^{\circ} C$. The temperature is reduced to $10^{\circ} C$. The density is increased from $1.1 \ g \ cm^{-3}$ to $1.15 \ g \ cm^{-3}$. What is the $\%$ change of molarity of the solution?