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Molar Mass, Molecular Weight and Elemental Composition Calculator


Molar mass of As2O3 is 197.84140 ± 0.00094 g/mol
Compound name is arsenic(iii) oxide

Convert between As2O3 weight and moles
CompoundMolesWeight, g
As2O3

Elemental composition of As2O3
ElementSymbolAtomic weightAtomsMass percent
ArsenicAs74.92160275.7391
OxygenO15.9994324.2609

Mass percent compositionAtomic percent composition

Sample reactions for As2O3
EquationReaction type
As2O3 + HCl = AsCl3 + H2Odouble replacement
As2O3 + H2S = As2S3 + H2Odouble replacement
As2O3 + C = CO2 + Assingle replacement
As2O3 + C = As + COsingle replacement
As2O3 + H2O = H3AsO3synthesis

Formula in Hill system is As2O3

Computing molar mass (molar weight)

To calculate molar mass of a chemical compound enter its formula and click 'Compute'. In chemical formula you may use:
  • Any chemical element. Capitalize the first letter in chemical symbol and use lower case for the remaining letters: Ca, Fe, Mg, Mn, S, O, H, C, N, Na, K, Cl, Al.
  • Functional groups: D, Ph, Me, Et, Bu, AcAc, For, Ts, Tos, Bz, TMS, tBu, Bzl, Bn, Dmg
  • parantesis () or brackets [].
  • Common compound names.
Examples of molar mass computations: NaCl, Ca(OH)2, K4[Fe(CN)6], CuSO4*5H2O, water, nitric acid, potassium permanganate, ethanol, fructose.

Molar mass calculator also displays common compound name, Hill formula, elemental composition, mass percent composition, atomic percent compositions and allows to convert from weight to number of moles and vice versa.

Computing molecular weight (molecular mass)

To calculate molecular weight of a chemical compound enter it's formula, specify its isotope mass number after each element in square brackets.
Examples of molecular weight computations: C[14]O[16]2, S[34]O[16]2.

Definitions of molecular mass, molecular weight, molar mass and molar weight

  • Molecular mass (molecular weight) is the mass of one molecule of a substance and is expressed in the unified atomic mass units (u). (1 u is equal to 1/12 the mass of one atom of carbon-12)
  • Molar mass (molar weight) is the mass of one mole of a substance and is expressed in g/mol.
Weights of atoms and isotopes are from NIST article.

Related: Molecular weights of amino acids
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