g What mass (in g) of a concentrated solution of nitric acid (69.0% HNO3 by mass) is needed to prepare 364.5 g of a 12.2% solution of HNO3 by mass?

64.4 g of concentrated nitric acid solution are needed.

Explanation:

First we calculate the mass of HNO₃ contained in 364.5 g of a 12.2% solution:

364.5 gsolution * 12.2 gHNO₃/100gsolution = 44.47 g HNO₃

Now we calculate how many grams of the concentrated solution would contain 44.47 grams of HNO₃:

44.47 g HNO₃ * 100 g solution / 69.0 = 64.45 g concentrated solution

So 64.4 g of concentrated nitric acid solution are needed.