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Molar Mass, Molecular Weight and Elemental Composition Calculator

Molar mass of KNO3 (Potassium nitrate) is 101.1032 g/mol

Convert between KNO3 weight and moles
CompoundMolesWeight, g

Elemental composition of KNO3
ElementSymbolAtomic weightAtomsMass percent

Computing molar mass step by step

First, compute the number of each atom in KNO3:
K: 1, N: 1, O: 3

Then, lookup atomic weights for each element in periodic table:
K: 39.0983, N: 14.0067, O: 15.9994

Now, compute the sum of products of number of atoms to the atomic weight:
Molar mass (KNO3) = ∑ Counti * Weighti =
Count(K) * Weight(K) + Count(N) * Weight(N) + Count(O) * Weight(O) =
1 * 39.0983 + 1 * 14.0067 + 3 * 15.9994 =
101.1032 g/mol

Mass percent compositionAtomic percent composition

Potassium nitrate appears as a white crystalline solid.

Sample reactions for KNO3
EquationReaction type
KNO3 = KNO2 + O2decomposition
KNO3 + H2CO3 = K2CO3 + HNO3double replacement
KNO3 + K = K2O + N2single replacement
NaCl + KNO3 = NaNO3 + KCldouble replacement
KNO3 = KNO2 + Odecomposition

Formula in Hill system is KNO3

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.

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