Printed from https://www.webqc.org

Molar Mass, Molecular Weight and Elemental Composition Calculator


Molar mass of water is 18.01528 ± 0.00044 g/mol
Compound name is water

Convert between H2O weight and moles
CompoundMolesWeight, g
H2O

Elemental composition of H2O
ElementSymbolAtomic weightAtomsMass percent
HydrogenH1.00794211.1898
OxygenO15.9994188.8102

Mass percent compositionAtomic percent composition

Sample reactions for H2O
EquationReaction type
Na + H2O = NaOH + H2single replacement
CO2 + H2O = C6H12O6 + O2double replacement
P4O10 + H2O = H3PO4synthesis
K + H2O = KOH + H2single replacement
Fe + H2O = Fe3O4 + H2single replacement

Formula in Hill system is H2O

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
molecular weights calculated today
Please let us know how we can improve this web app.
Menu Balance Molar mass Gas laws Units Chemistry tools Periodic table Chemical forum Symmetry Constants Contribute Contact us
How to cite?
Choose languageDeutschEnglishEspañolFrançaisItalianoNederlandsPolskiPortuguêsРусский中文日本語한국어