# What do we mean by percentage concentration?

"mass of solute"/"mass of solution"xx100% $=$ ??%. Thus $20 \cdot g$ of solute in $80 \cdot g$ of solvent (which is typically water) has a concentration of 20%(m/m). These can be converted to concentrations with units of $m o l \cdot {L}^{-} 1$ PROVIDED we have the density of the solution. Anyway, you will have to specify the terms of your concentration.