Question

Molarity of liquid $HCl$ will be, if density of solution is $1.17gm/cc$?

Answer 1

Molarity represents the strength of a substance in solution. It is the ratio of the moles of solute dissolved in a litre of solution.

Complete step by step answer: $HCl$ is hydrochloric acid whose density is $1.17gm/cc$. We know that $1cc$ is equal to $1mL$as $cc$ and $mL$ are different names of the same volume. The unit $cc$ stands for cubic centimeters and $mL$ stands for milliliters.
$1mL$ of $HCl$ contains $1.17gm$. Therefore $1L$ or $1000mL$ of $HCl$ contains $1.17 \times 1000$= $1170gm$.
In order to determine the moles of $HCl$ present in $1170gm$ we need to determine the molar or molecular mass of $HCl$.
Molar mass of $HCl$ = atomic mass of $H$ + atomic mass of $Cl$.
$\Rightarrow$ $1 + 35.5$ = $36.5gm$.
Thus the moles of $HCl$ in $1170gm$ = $\dfrac{{weight{\text{ }}of{\text{ }}HCl}}{{molar{\text{ }}mass{\text{ }}of{\text{ }}HCl}}$
$\Rightarrow$ $\dfrac{{1170}}{{36.5}}$ = $32.05moles$.
As, morality is determined as the ratio of number of moles and volume of solution in litre, so the molarity of $HCl$ liquid will be
Molarity = $\dfrac{{no.{\text{ }}of{\text{ }}moles}}{{volume{\text{ }}in{\text{ }}litre}}$
$\Rightarrow$ $\dfrac{{32.05}}{1}$ = $32.05M$.

Note: Molarity is also referred to as molar concentration of a solution. Similar term molality should not be confused with morality. Molarity is expressed in upper case as $M$ and molality is expressed in lower case as $m$. The basic difference between the two lies in mass vs. volume. Molality is the ratio of moles of solute dissolved in kilograms of solvent. So the unit is $mol/kg$ or $m$. Both are the measure of a substance concentration in solution. Density is the measure of compactness of a substance in solid, liquid or gas phase. It is the ratio of mass and volume of the substance. So more the density of a substance less will be the volume and vice versa. The density of water is $1gm/mL$.