Molar Mass of O (Oxygen)

Molar Mass Calculator
Chemical formula Write symbols with a capital letter: CoCl2 is cobalt chloride, COCl2 is phosgene. A hydrate takes a dot: CuSO4·5H2O or CuSO4.5H2O

What is the molar mass of O?

Answer

M(O) =
15.999 g/mol

Atomic weights: IUPAC standard values (CIAAW, 2024).

Elemental oxygen is made of O2 molecules: M(O2) = 31.998 g/mol = 0.031998 kg/mol.

Contribution of each element
Element Atoms, n Atomic weight, A n × A, g/mol Mass fraction, w
Ooxygen115.99915.999 w = 100.00%

Atomic weights: CIAAW, Abridged Standard Atomic Weights (2024)

See Also

Recalculate with different values ↑

Neighbouring elements of the periodic table

FormulaM, g/mol
B (boron)10.81
C (carbon)12.011
N (nitrogen)14.007
O (oxygen)15.999
F (fluorine)18.998
Ne (neon)20.180
Na (sodium)22.990

FAQ

What is the molar mass of O?

M(O) = 15.999 g/mol

Why is the molar mass of oxygen 15.999 and not 32?

15.999 g/mol is the mass of one mole of O atoms. Elemental oxygen is made of O₂ molecules: M(O₂) = 2 × 15.999 = 31.998 g/mol (32 in school problems); in SI units, 0.031998 kg/mol. In a problem about the gas, the molar mass of oxygen is usually M(O₂).

How many grams are in 2 moles of O?

m = n × M = 2 mol × 15.999 g/mol = 31.998 g.

See Also