What is percent concentration by mass?

Answer 1

Percent concentration by mass is the mass of the item of interest divided by the total mass times 100%. So, percent concentration by mass of NaCl of a solution made by dissolving 10 g NaCl in 100 g water would be 10 g NaCl/(10 g + 100 g) = 10 g/110 g = 0.0909 and then x100% = 9.09% by mass