Question

The concentrated sulphuric acid that is peddled commercial is 95% $H_2SO_4$ by weight. If the density of this commercial acid is $1.834\, g$ $cm^{-3}$, the molarity of this solution is

• A. $17.8\, M$
• B. $12.0\, M$
• C. $10.5\, M$
• D. $15.7\, M$

Answer 1

Answer: (A)

$95\%\, H_2SO_4$ by weight means $100g\, H_2SO_4$ solution contains $95g \,H_2SO_4$ by mass. Molar mass of $H_2SO_4 = 98g\, mol^{-1}$
Moles in $95g=\frac{95}{98}=0.969$ mole
Volume of $100g\, H_2SO_4$
$=\frac{mass}{density}=\frac{100g}{1.834g\,cm^{-3}}$
$= 54.52 \,cm^{3} = 54.52 \times 10^{-}3\, L$
$Molarity=\frac{Moles\, of \,solute}{Volme\, of\, solut\, in \,L}$
$=\frac{0.969}{54.52\times10^{-3}}=17.8\,M$