If the mole fraction of ethanol in a solution of ethanol in water is $0.050$,then find the molarity of the given solution. (in $M$)

$A$ 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.

$1 \ g$ of a solute is added to $18 \ g$ of water. In this aqueous solution,what is the mass per cent of the solute (in $\%$)?

$10 \ g$ of $NaOH$ is dissolved in $500 \ mL$ of aqueous solution. Calculate the molarity of this solution? (Given,formula weight of $NaOH = 40$)

$A$ compound $H_2X$ with molar weight of $80 \ g \ mol^{-1}$ is dissolved in a solvent having density of $0.4 \ g \ mL^{-1}$. Assuming no change in volume upon dissolution,the molality of a $3.2 \ M$ solution is:

Define the following terms:
$(i)$ Mole fraction $(ii)$ Molality $(iii)$ Molarity $(iv)$ Mass percentage