Final answer:
The molar mass of an oxygen atom is approximately 16.00 g/mol, while the molar mass of an oxygen molecule (O₂), which is how oxygen typically exists, is about 32.00 g/mol.
Step-by-step explanation:
The molar mass of an element is the mass of one mole of that element. The molar mass of oxygen is determined by looking at the standard atomic mass on the periodic table. The atomic mass of oxygen is approximately 15.999 grams per mole, which is usually rounded to 16.00 g/mol for most calculations, making (b) 16.00 g/mol the correct answer for the molar mass of a single oxygen atom. However, it's important to note that oxygen usually exists as a diatomic molecule (O₂), so when we refer to oxygen gas, we double this amount, resulting in a molar mass of about 32.00 g/mol.