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A commercially sold conc. \mathrm{HCl}$ is $35 \% \mathrm{HCl}  by mass. If the density of this commercial acid is \mathrm{1.46\: g/mL,}  the molarity of this solution is :
(Atomic mass : \mathrm{Cl}=35.5\, \mathrm{amu}, \mathrm{H}=1 \mathrm{amu} )

Option: 1

10.2 \mathrm{~M}


Option: 2

12.5 \mathrm{~M}


Option: 3

14.0 \mathrm{~M}


Option: 4

18.2 \mathrm{~M}


Answers (1)

best_answer

Given,

Concentration of \mathrm{HCl}=35 \% \mathrm{HCl} by mass.
\mathrm{density =1.46 \mathrm{~g} / \mathrm{ml}}

Let us assume the total volume of Solution \mathrm{\mathrm{=1000\, \mathrm{ml}}}

From density, total mass of Solution \mathrm{=1.46 \times 1000=1460 ~g}

\mathrm{\therefore\: mass \: of\: \mathrm{HCl}=\frac{35}{100} \times 1460=511~g}

\mathrm{\text{numeber of moles of }\: \mathrm{HCl}=\frac{\text { mass of } \mathrm{HCl} \text { in Solution }}{\text { molar mass of HCl }}}
                                                         \mathrm{=\frac{511}{36.5}=14}

\mathrm{Molarity = \text{no. of moles of}\: \mathrm{HCl} \: in \: 1000 \mathrm{ml}\: \: of \: solution}
                    \mathrm{=14 {~M}}

Hence, option (C) is correct.

Posted by

manish

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