The molality of $648 \ g$ of pure water is .................. $m$.

$3.1 \ g$ of a compound,'$X$' (molar mass $= 62 \ g \ mol^{-1}$) is dissolved in $19.5 \ g$ of other compound,$Y$ (molar mass $= 78 \ g \ mol^{-1}$). The ratio of mole fractions of $X$ and $Y$ in the solution is

Match List-$I$ with List-$II$.

List-$I$ (Example)	List-$II$ (Type of Solution)
$A$. Humidity	$I$. Solid in solid
$B$. Alloys	$II$. Liquid in gas
$C$. Amalgams	$III$. Solid in gas
$D$. Smoke	$IV$. Liquid in solid

Choose the correct answer from the options given below:

If the molarity and molality of an aqueous solution of $H_2SO_4$ are $1.56 \ M$ and $1.8 \ m$ respectively,what is the density of the solution in $g/mL$?

Calculate the amount of benzoic acid $(C_{6}H_{5}COOH)$ required for preparing $250 \ mL$ of $0.15 \ M$ solution in methanol.

In a water sample,the concentration of $F^-$ ions is $10 \ ppm$ by weight-volume. What is the concentration of $F^-$ in $\% W/V$ in that solution?