In a solution of $7.8 \ g$ benzene $(C_6H_6)$ and $46.0 \ g$ toluene $(C_6H_5CH_3)$,the mole fraction of benzene in this solution is:

$3.0 \ g$ ethanoic acid in $50 \ g$ benzene has . . . . . . molality. (Atomic weights: $H=1, C=12, O=16$).

$A$ sample of drinking water was found to be severely contaminated with chloroform,$CHCl_{3}$,supposed to be carcinogenic in nature. The level of contamination was $15 \ ppm$ (by mass).
$(i)$ Express this in percent by mass.
$(ii)$ Determine the molality of chloroform in the water sample.

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? $(N=14 \ u, O=16 \ u, H=1 \ u)$

The molarity of the solution when $4.9 \ g$ of $H_2SO_4$ is dissolved in $250 \ mL$ of solution is: (in $M$)

If $100 \ g$ of a $0.2 \ m$ aqueous solution is diluted by adding $200 \ g$ of water,what will be the molality of the resulting solution?