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# Concentrated nitric acid used in laboratory work is 68% nitric acid by mass in aqueous solution. What should be the molarity of such a sample of the acid if the density of the solution is $1.504 g mL^{–1}$?

$\begin{array}{1 1}16.23M\\18.23M\\17.23M\\20.23M\end{array}$

68% nitric acid by mass means that
Mass of nitric acid = 68g
Mass of solution = 100g
Molar mass of $HNO_3=63 gmol^{-1}$
$\therefore$ 68 g $HNO_3=\large\frac{68}{63}$ mole =1.079 mole
Density of solution =$1.504gmL^{-1}$
$\therefore$ Volume of solution =$\large\frac{100}{1.504}$mL
$\Rightarrow$ 66.5mL=0.0665 L
Molarity of the solution =$\large\frac{\text{Moles of the solute}}{\text{Volume of solution}}$
$\Rightarrow \large\frac{1.079}{0.0665}$M =16.23M