What is the molar mass of oxygen?

Just to clarify the previous answer with some additional context - the exact molar mass is actually 15.999 g/mol for oxygen atoms according to IUPAC standards, but most chemistry classes and textbooks round it to 16.00 g/mol for calculation purposes.

The reason oxygen forms O₂ molecules is because it's more stable that way - each oxygen atom has 6 valence electrons and sharing two electrons through a double bond gives both atoms a full octet.

Fun fact: There's also ozone (O₃) which has a molar mass of about 48 g/mol, but when people ask about "oxygen" they usually mean O₂ unless specified otherwise.

If you're doing lab work or precise calculations, you might want to use the more accurate value, but for most high school and college chemistry problems, 32.00 g/mol for O₂ is perfectly acceptable.

The molar mass of oxygen depends on whether you're talking about oxygen atoms or oxygen molecules!

For oxygen atoms (O), the molar mass is 16.00 g/mol. This comes from the atomic mass of oxygen, which is approximately 16 atomic mass units.

However, in nature, oxygen typically exists as diatomic molecules (O₂), so the molar mass of oxygen gas is 32.00 g/mol (since 16 × 2 = 32).

This is super important in chemistry calculations because if you're working with O₂ gas in reactions, you need to use 32 g/mol for your stoichiometry problems. I remember messing this up on a test back in school - my teacher kept emphasizing "know whether you're dealing with atoms or molecules!"