The molarity of a solution of $Na_2CO_3$ having $10.6 \ g$ in $500 \ mL$ of solution is ......... $M$.

$A$ sample of drinking water is found to be severely contaminated with chloroform $(CHCl_3)$,which is a suspected carcinogen. The level of contamination is $15 \ ppm$ (by mass). Calculate the molarity of chloroform in the water sample.

The $ppm$ level of $F^{-}$ in a $500 \ g$ sample of a toothpaste containing $0.2 \ g$ $F^{-}$ is:

$1 \, M$ solution contains

If $15 \ g$ of $NaOH$ is dissolved in water to make $250 \ mL$ of solution,find the molarity of this solution in $M$.

$3.0\, g$ of oxalic acid $[(CO_2H)_2 \cdot 2H_2O]$ is dissolved in a solvent to prepare a $250\, mL$ solution. The density of the solution is $1.9\, g/mL$. The molality and normality of the solution,respectively,are closest to