What is the molarity of a solution containing $0.8 \ g$ of $NaOH$ (molar mass $40 \ g \ mol^{-1}$) in $150 \ cm^{3}$ of water?

Define mole fraction.

$250 \, mL$ of a sodium carbonate solution contains $2.65 \, g$ of $Na_2CO_3$. If $10 \, mL$ of this solution is diluted to $1 \, L$,what is the concentration of the resultant solution? (Molecular weight of $Na_2CO_3 = 106$)

What is the mass of the solute in $g$ in $1 \ L$ of a solution having $40\%$ concentration by weight? The density of the solution is $1.2 \ g/mL$.

If $5.85 \ g$ of $NaCl$ is dissolved in $90 \ g$ of water,then find out the mole fraction of $NaCl$.

The number of units,which are used to express the concentration of solutions from the following,is $.......$ Mass percent,Mole,Mole fraction,Molarity,ppm,Molality.