concentration as a mass percentage is the percentage of mass of solute from the whole mass of the mixture whole mass of the mixture - 50.0 g + 150.0 g = 200.0 g mass of solute - 50.0 g mass percentage = mass of NaCl / mass of total mixture x 100% w/w % = 50.0 g / 200.0 g x 100 % = 25 % mass percentage of NaCl is 25 %
