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Molar Mass, Molecular Weight and Elemental Composition Calculator

Molar mass of SO2 (Sulfur dioxide) is 64.0638 g/mol

Convert between SO2 weight and moles
CompoundMolesWeight, g

Elemental composition of SO2
ElementSymbolAtomic weightAtomsMass percent

Computing molar mass step by step

First, compute the number of each atom in SO2:
S: 1, O: 2

Then, lookup atomic weights for each element in periodic table:
S: 32.065, O: 15.9994

Now, compute the sum of products of number of atoms to the atomic weight:
Molar mass (SO2) = ∑ Counti * Weighti =
Count(S) * Weight(S) + Count(O) * Weight(O) =
1 * 32.065 + 2 * 15.9994 =
64.0638 g/mol

Mass percent compositionAtomic percent composition

Sulfur dioxide is a colorless gas with a pungent odor.

Sample reactions for SO2
EquationReaction type
SO2 + O2 = SO3synthesis
C + SO2 = CS2 + COdouble replacement
SO2 + H2O = H2SO3synthesis
SO2 + O2 + H2O = H2SO4synthesis
H2S + SO2 = S + H2Odouble replacement

Formula in Hill system is O2S

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, caffeine.

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
molecular weights calculated today
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