If the atomic mass of 1 oxygen atom is 15.9994 amu, how much mass does of 1 mole oxygen have?

15.9994 amu

Explanation:

By definition 1 mole of any substance is the mass that contains 1 Avogadro's Number of particle. (=> 6.02 x 10²³ particles/mole).

1 mole Oxy = > 15.9994 amu = > contains 6.02 x 10²³ particles Oxy / mole

1 mole Sulfur = > 32.064 amu = > contains 6.02 x 10²³ particles Sulfur / mole

1 mole H₂O = > 18 amu = > contains 6.02 x 10²³ molecules of water / mole.