To calculate the molar mass of HNO3, we need to add up the atomic masses of each element present in the compound.

The atomic mass of Hydrogen (H) is approximately 1.008 grams per mole.

The atomic mass of Nitrogen (N) is approximately 14.01 grams per mole.

The atomic mass of Oxygen (O) is approximately 16.00 grams per mole.

Since there is one Hydrogen atom, one Nitrogen atom, and three Oxygen atoms in HNO3, the molar mass can be calculated as follows:

Molar mass of HNO3 = (1 x 1.008 g/mol) + (1 x 14.01 g/mol) + (3 x 16.00 g/mol)

Molar mass of HNO3 = 1.008 g/mol + 14.01 g/mol + 48.00 g/mol

Molar mass of HNO3 = 63.018 g/mol

Therefore, the molar mass of HNO3 is approximately 63.018 grams per mole.