How much water should be added to 15g of NaCl to obtain 15℅ of salt solution ?
The mass by mass percentage of a solution is given by the following relation
where mass of solution = mass of solute + mass of solution
Here, mass of the solute (i.e. salt) = 15 g and the required concentration of the solution is 15 %.
Let the mass of water be a grams.
15 = [15 / (15 + a)] X 100
Solving for a, we get
a = (100 - 15)g = 85 g