The molarity of $0.006 \ mol$ of $NaCl$ in $100 \ mL$ solution is (in $M$)

How many grams of ethanol must be added to $1.0 \ kg$ of water to have a mole fraction of ethanol equal to $0.2$?

$V_1 \ \text{c.c.}$ of a solution having molarity $M_1$ is diluted to have molarity $M_2$. The volume of water required to be added will be $:-$

The hardness of a water sample due to $MgSO_4$ is $50 \, ppm$. Calculate the amount of $MgSO_4$ in $mg$ present in $1 \, kg$ of water.

Calculate the mole fraction of solute in the solution if the solution is prepared by dissolving $394 \ g$ of a nonvolatile solute in $622 \ g$ of water at $30^{\circ}C$ (Molar mass of solute $= 342 \ g \ mol^{-1}$).

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