$63 \ g$ of a compound (Mol. Wt. $= 126$) was dissolved in $500 \ g$ of distilled water. The density of the resultant solution is $1.126 \ g / mL$. The molarity of the solution is: (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.

Molality $(m)$ of $3 \text{ M}$ aqueous solution of $NaCl$ is:
(Given: Density of solution = $1.25 \text{ g mL}^{-1}$, Molar mass in $\text{g mol}^{-1}$: $Na = 23$, $Cl = 35.5$) (in $\text{m}$)

Nalorphene $(C_{19}H_{21}NO_{3})$,similar to morphine,is used to combat withdrawal symptoms in narcotic users. The dose of nalorphene generally given is $1.5 \, mg$. Calculate the mass of $1.5 \times 10^{-3} \, m$ aqueous solution required for the above dose.

$1 \, M$ solution contains

What is meant by the concentration of a solution?