If the density of a solution is $1.17 \, g/cc$,what is the molarity of liquid $HCl$?

Calculate the mole fraction of benzene in a solution containing $30\%$ by mass in carbon tetrachloride.

Molarity is expressed as

The molality of a $10\%\ (v/v)$ solution of di-bromine in $CCl_4$ (carbon tetrachloride) is $x$. $x = ...... \times 10^{-2}\ m$. (Nearest integer)
[Given : molar mass of $Br_2 = 160\ g\ mol^{-1}$
atomic mass of $C = 12\ g\ mol^{-1}$
atomic mass of $Cl = 35.5\ g\ mol^{-1}$
density of dibromine $= 3.2\ g\ cm^{-3}$
density of $CCl_4 = 1.6\ g\ cm^{-3}$]

The concentration of $1 \ L$ of $CaCO_3$ solution is $1000 \ ppm$. What is its concentration in $mol \ L^{-1}$ ?
$(Ca=40 \ u, O=16 \ u, C=12 \ u)$

If a substance $A$ dissolves in a solution of a mixture of $B$ and $C$ with their respective number of moles as $n_A, n_B$ and $n_C$,the mole fraction of $C$ in the solution is: