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Molar Mass, Molecular Weight and Elemental Composition Calculator

Molar mass of LaCePrNdPmSmEuGdTbDyHoErTmYbLuAcThPaUNpPuAmCmBkCfEsFm is 5230.8957 g/mol

Convert between LaCePrNdPmSmEuGdTbDyHoErTmYbLuAcThPaUNpPuAmCmBkCfEsFm weight and moles
CompoundMolesWeight, g
LaCePrNdPmSmEuGdTbDyHoErTmYbLuAcThPaUNpPuAmCmBkCfEsFm

Elemental composition of LaCePrNdPmSmEuGdTbDyHoErTmYbLuAcThPaUNpPuAmCmBkCfEsFm
ElementSymbolAtomic weightAtomsMass percent
LanthanumLa138.9054712.6555
CeriumCe140.11612.6786
PraseodymiumPr140.9076512.6938
NeodymiumNd144.24212.7575
PromethiumPm144.91274912.7703
SamariumSm150.3612.8745
EuropiumEu151.96412.9051
GadoliniumGd157.2513.0062
TerbiumTb158.9253513.0382
DysprosiumDy162.50013.1065
HolmiumHo164.9303213.1530
ErbiumEr167.25913.1975
ThuliumTm168.9342113.2295
YtterbiumYb173.05413.3083
LutetiumLu174.966813.3449
ActiniumAc227.02775214.3401
ThoriumTh232.0380614.4359
ProtactiniumPa231.0358814.4168
UraniumU238.0289114.5504
NeptuniumNp236.0465714.5125
PlutoniumPu238.04956014.5508
AmericiumAm241.05682914.6083
CuriumCm243.06138914.6466
BerkeliumBk247.07030714.7233
CaliforniumCf249.07485314.7616
EinsteiniumEs252.0829814.8191
FermiumFm257.09510514.9149

Computing molar mass step by step

First, compute the number of each atom in LaCePrNdPmSmEuGdTbDyHoErTmYbLuAcThPaUNpPuAmCmBkCfEsFm:
La: 1, Ce: 1, Pr: 1, Nd: 1, Pm: 1, Sm: 1, Eu: 1, Gd: 1, Tb: 1, Dy: 1, Ho: 1, Er: 1, Tm: 1, Yb: 1, Lu: 1, Ac: 1, Th: 1, Pa: 1, U: 1, Np: 1, Pu: 1, Am: 1, Cm: 1, Bk: 1, Cf: 1, Es: 1, Fm: 1

Then, lookup atomic weights for each element in periodic table:
La: 138.90547, Ce: 140.116, Pr: 140.90765, Nd: 144.242, Pm: 144.912749, Sm: 150.36, Eu: 151.964, Gd: 157.25, Tb: 158.92535, Dy: 162.5, Ho: 164.93032, Er: 167.259, Tm: 168.93421, Yb: 173.054, Lu: 174.9668, Ac: 227.0277521, Th: 232.03806, Pa: 231.03588, U: 238.02891, Np: 236.04657, Pu: 238.0495599, Am: 241.0568291, Cm: 243.0613891, Bk: 247.070307, Cf: 249.0748535, Es: 252.08298, Fm: 257.095105

Now, compute the sum of products of number of atoms to the atomic weight:
Molar mass (LaCePrNdPmSmEuGdTbDyHoErTmYbLuAcThPaUNpPuAmCmBkCfEsFm) = ∑ Counti * Weighti =
Count(La) * Weight(La) + Count(Ce) * Weight(Ce) + Count(Pr) * Weight(Pr) + Count(Nd) * Weight(Nd) + Count(Pm) * Weight(Pm) + Count(Sm) * Weight(Sm) + Count(Eu) * Weight(Eu) + Count(Gd) * Weight(Gd) + Count(Tb) * Weight(Tb) + Count(Dy) * Weight(Dy) + Count(Ho) * Weight(Ho) + Count(Er) * Weight(Er) + Count(Tm) * Weight(Tm) + Count(Yb) * Weight(Yb) + Count(Lu) * Weight(Lu) + Count(Ac) * Weight(Ac) + Count(Th) * Weight(Th) + Count(Pa) * Weight(Pa) + Count(U) * Weight(U) + Count(Np) * Weight(Np) + Count(Pu) * Weight(Pu) + Count(Am) * Weight(Am) + Count(Cm) * Weight(Cm) + Count(Bk) * Weight(Bk) + Count(Cf) * Weight(Cf) + Count(Es) * Weight(Es) + Count(Fm) * Weight(Fm) =
1 * 138.90547 + 1 * 140.116 + 1 * 140.90765 + 1 * 144.242 + 1 * 144.912749 + 1 * 150.36 + 1 * 151.964 + 1 * 157.25 + 1 * 158.92535 + 1 * 162.5 + 1 * 164.93032 + 1 * 167.259 + 1 * 168.93421 + 1 * 173.054 + 1 * 174.9668 + 1 * 227.0277521 + 1 * 232.03806 + 1 * 231.03588 + 1 * 238.02891 + 1 * 236.04657 + 1 * 238.0495599 + 1 * 241.0568291 + 1 * 243.0613891 + 1 * 247.070307 + 1 * 249.0748535 + 1 * 252.08298 + 1 * 257.095105 =
5230.8957 g/mol


Mass percent compositionAtomic percent composition

Formula in Hill system is AcAmBkCeCfCmDyErEsEuFmGdHoLaLuNdNpPaPmPrPuSmTbThTmUYb

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, T, Ph, Me, Et, Bu, AcAc, For, Tos, Bz, TMS, tBu, Bzl, Bn, Dmg
  • parenthesis () or brackets [].
  • Common compound names.
Examples of molar mass computations: NaCl, Ca(OH)2, K4[Fe(CN)6], CuSO4*5H2O, nitric acid, potassium permanganate, ethanol, fructose, caffeine, water.

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

  • 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.
  • Mole is a standard scientific unit for measuring large quantities of very small entities such as atoms and molecules. One mole contains exactly 6.022 ×1023 particles (Avogadro's number)

Steps to calculate molar mass

  1. Identify the compound: write down the chemical formula of the compound. For example, water is H2O, meaning it contains two hydrogen atoms and one oxygen atom.
  2. Find atomic masses: look up the atomic masses of each element present in the compound. The atomic mass is usually found on the periodic table and is given in atomic mass units (amu).
  3. Calculate molar mass of each element: multiply the atomic mass of each element by the number of atoms of that element in the compound.
  4. Add them together: add the results from step 3 to get the total molar mass of the compound.

Example: calculating molar mass

Let's calculate the molar mass of carbon dioxide (CO2):

  • Carbon (C) has an atomic mass of about 12.01 amu.
  • Oxygen (O) has an atomic mass of about 16.00 amu.
  • CO2 has one carbon atom and two oxygen atoms.
  • The molar mass of carbon dioxide is 12.01 + (2 × 16.00) = 44.01 g/mol.

Lesson on computing molar mass

Weights of atoms and isotopes are from NIST article.

Related: Molecular weights of amino acids

molecular weights calculated today
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