SOLUTION: I need an equation for finding the unknown mass to add a substance to a solution, when you have a target concentration. Ex: I have a solution that weighs 12.0 grams on a balance

Question 634177: I need an equation for finding the unknown mass to add a substance to a solution, when you have a target concentration.
Ex: I have a solution that weighs 12.0 grams on a balance and I need to know how much mass of a substance to add that nets me 24% by weight of that additional substance in the final solution. (assume sg is =1.0). I am not looking for specifics in molarity or molality.
Answer by richwmiller(17219) (Show Source): You can put this solution on YOUR website!
If you want the other substance to be 24% then .76x=12
76x=1200
x=300/19
If you want the 12 grams to be 24% then
.24x=12
24x=1200
x=50

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