$30 \ mL$ of $0.5 \ M$ $NaOH$ is diluted to $500 \ mL$ by adding water. What will be the molarity of the diluted solution (in $M$)?

$x \ g$ of water is mixed in $69 \ g$ of ethanol. The mole fraction of ethanol in the resultant solution is $0.6$. What is the value of $x$ in grams?

$3.42 \times 10^{-2} \ kg$ of sugar (molar mass $342 \ g \ mol^{-1}$) is dissolved in water to produce $234.2 \ g$ of sugar syrup. What is the molality of the sugar syrup?

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: At $10^{\circ} C$,the density of a $5 \ M$ solution of $KCl$ is given. The solution is cooled to $-21^{\circ} C$. The molality of the solution will remain unchanged.
Reason $R$: The molality of a solution does not change with temperature as mass remains unaffected by temperature.
In the light of the above statements,choose the correct answer from the options given below:

Sea water,which can be considered as a $6 \ M$ solution of $NaCl$,has a density of $2 \ g \ mL^{-1}$. The concentration of dissolved oxygen $(O_2)$ in sea water is $5.8 \ ppm$. Then the concentration of dissolved oxygen $(O_2)$ in sea water is $x \times 10^{-4} \ m$. $x = ............$ $(Nearest \ integer)$
Given: Molar mass of $NaCl$ is $58.5 \ g \ mol^{-1}$. Molar mass of $O_2$ is $32 \ g \ mol^{-1}$.

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