Molar Mass of O2 (Oxygen)

Molar Mass Calculator

What is the molar mass of O₂?

Answer

M(O₂) =

31.998 g/mol

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

One O atom: M(O) = 15.999 g/mol; O₂ is two atoms.

Contribution of each element
Element	Atoms, n	Atomic weight, A	n × A, g/mol Mass fraction, w	Mass fraction, w
Ooxygen	2	15.999	31.998 w = 100.00%	100.00%

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

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Molar Mass of O (Oxygen): Step by Step

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Molar masses of substances nearby

Formula	M, g/mol
C₂H₆ (ethane)	30.070
P (phosphorus)	30.974
CH₅N (methylamine)	31.058
O₂ (oxygen)	31.998
CH₃OH (methanol)	32.042
N₂H₄ (hydrazine)	32.046
S (sulfur)	32.06

FAQ

What is the molar mass of O2?

M(O₂) = 31.998 g/mol

How to calculate the molar mass of O₂?

Add up the atomic weights of all the atoms in the formula: 2 × 15.999 = 31.998 g/mol.

How many grams are in 2 moles of O₂?

m = n × M = 2 mol × 31.998 g/mol = 63.996 g.

See Also