Molar Mass of H3PO3 (Phosphonic Acid)

Molar Mass Calculator

What is the molar mass of H₃PO₃?

Answer

M(H₃PO₃) =

81.995 g/mol

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

Contribution of each element
Element	Atoms, n	Atomic weight, A	n × A, g/mol Mass fraction, w	Mass fraction, w
Hhydrogen	3	1.0080	3.0240 w ≈ 3.69%	≈ 3.69%
Pphosphorus	1	30.974	30.974 w ≈ 37.78%	≈ 37.78%
Ooxygen	3	15.999	47.997 w ≈ 58.54%	≈ 58.54%
Σ = 81.995 g/mol w = 100%				100%

Each fraction is rounded on its own, so the printed ones add up to 100.01%; unrounded, they make exactly 100%.

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

Mass fractions of the elements

O 58.54%P 37.78%

H 3.69%

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Molar masses of substances nearby

Formula	M, g/mol
HBr (hydrogen bromide)	80.912
H₂Se (hydrogen selenide)	80.987
ZnO (zinc oxide)	81.38
H₃PO₃ (phosphonic acid)	81.995
CH₃COONa (sodium acetate)	82.034
H₂SO₃ (sulfurous acid)	82.07
C₆H₁₀ (cyclohexene)	82.146

FAQ

What is the molar mass of H3PO3?

M(H₃PO₃) = 81.995 g/mol

How to calculate the molar mass of H₃PO₃?

Add up the atomic weights of all the atoms in the formula: 3 × 1.0080 + 30.974 + 3 × 15.999 = 81.995 g/mol.

How many grams are in 2 moles of H₃PO₃?

m = n × M = 2 mol × 81.995 g/mol = 163.990 g.

See Also