Calculate the amount of substance in 12.5 g of nitric acid?

Decision:
we will use the formula to calculate the amount of substance
N = m / M, where m is the mass of the substance, and M is the molar mass
the nitric acid formula contains one hydrogen atom with a molar mass M (H) = 1, one nitrogen atom with a molar mass M (N) = 7, and three oxygen molecules with a molar mass M (O) = 8, we get
M (HNO3) = M (H) + M (N) + 3 * M (O) = 32, hence
N (HNO3) = 12.5 / 32 = 0.3906 mol
Answer: The molar mass of nitric acid is 0.3906 mol