What is the sum of the mole fractions of all the components in a solution?

If $15 \ g$ of $NaOH$ is dissolved in water to make $250 \ mL$ of solution,find the molarity of this solution in $M$.

The density of a stock solution of $29.2\% \, (w/w) \, HCl$ is $1.25 \, g \, mL^{-1}$. If the molar mass of $HCl$ is $36.5 \, g \, mol^{-1}$,what volume (in $mL$) of the stock solution is required to prepare $200 \, mL$ of $0.4 \, M \, HCl$ solution?

$A$ $2.0 \, M$ solution is obtained when $0.5 \, mole$ of solute is dissolved in:

What is the physical state of a solution containing camphor as the solute and $N_2$ gas as the solvent?

What is the molarity of a $1 \ L$ solution of $93\% \ (w/v)$ $H_2SO_4$ (in $M$)? The density of the solution is $1.84 \ g/mL$.