Molar Mass of SO3 (Sulfur Trioxide)

Molar Mass Calculator

What is the molar mass of SO₃?

Answer

M(SO₃) ≈

80.06 g/mol

Atomic weights: IUPAC standard values (CIAAW, 2024); the sum is rounded to the decimal places of the least precise one — S: 32.06.

Contribution of each element
Element	Atoms, n	Atomic weight, A	n × A, g/mol Mass fraction, w	Mass fraction, w
Ssulfur	1	32.06	32.06 w ≈ 40.05%	≈ 40.05%
Ooxygen	3	15.999	47.997 w ≈ 59.95%	≈ 59.95%
Σ = 80.057 ≈ 80.06 g/mol w = 100%				100%

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

Mass fractions of the elements

O 59.95%S 40.05%

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Molar masses of substances nearby

Formula	M, g/mol
TiO₂ (titanium dioxide)	79.865
Br (bromine)	79.904
NH₄NO₃ (ammonium nitrate)	80.043
SO₃ (sulfur trioxide)	80.06
HBr (hydrogen bromide)	80.912
H₂Se (hydrogen selenide)	80.987
ZnO (zinc oxide)	81.38

FAQ

What is the molar mass of SO3?

M(SO₃) ≈ 80.06 g/mol

How to calculate the molar mass of SO₃?

Add up the atomic weights of all the atoms in the formula: 32.06 + 3 × 15.999 = 80.057 ≈ 80.06 g/mol.

How many grams are in 2 moles of SO₃?

m = n × M = 2 mol × 80.06 g/mol = 160.12 g.

See Also