1000 g of 55%(mass percentage) nitric acid solution is to be diluted to 20%(mass percentage) nitric acid solution. How many liters of water should be added to the starting solution?

Answer 1

1000 g that is 55% by mass means you have 550 g HNO3 in the 1000 g.

So 550 g add to X water = 20%?
550/X)*100 = 20
Solve for X = 550/0.2 = 2750 g

The correct way to do it is to start with 1000 g of the 55% stuff and add water until the mass is 2750 g.