Find the number of molecules contained in 126 g of nitric acid?

m (HNO3) = 126 g.
Let’s determine the number of nitric acid molecules. To do this, first determine the amount of substance. We write down the solution.
n = m / M.
M (HNO3) = 1 + 14 + 3 × 16 = 63 g / mol.
n = 126 g / 63 g / mol = 2 mol.
This means that the amount of nitric acid substance is 2 mol. Next, we find the number of nitric acid molecules.
N = Na × n.
Where Na is Avogadro’s number, equal to 6.02 × 10 ^ 23 molecules.
N = 2 mol × 6.02 × 10 ^ 23 = 12.04 × 10 ^ 23 molecules.
This means that the number of molecules of nitric acid with a mass equal to 126 g is 12.04 × 10 ^ 23 molecules.
Answer: N = 12.04 × 10 ^ 23 molecules.