Molar mass

Calculation of the molar mass (or molecular weight) of atoms and molecules.
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Allowed: letters, numbers, parentheses

This tool is a molar mass calculator.

The tool calculates in order of priority:
- 1st field: the molar mass of the selected atom (choice from the 118 elements of the periodic table).
- 2nd field: the molecule mass of the selected molecule (choice from a list of common molecules)
- 3rd field: the molar mass of the formula entered (atom or molecule).

So, you need to choose "disable" field 1 to calculate field 2 and disable field 1 and 2 to calculate field 3.

Important Note
Do respect the uppercases and lowercases letters when you enter a chemical formula in the calculator above (3rd field). Thus,
- The symbol of an atom with a single letter is always written in capital letters. Examples: C, O and N not c, o and n.
- The symbol of an atom with two letters has the first letter in uppercase and the second in lowercase. Examples: Fe, Co and Xe not FE, CO, XE, fe, ce and xe.
If you type SI for Silicon instead of Si, then the calculator will interpret this formula as [Suffer (S) - Iodine (I)].

Definition of molar mass

The molar mass of an atomic or molecular chemical element is the mass of a mole of that substance. The symbol used is M and the common unit is g/mol (kg/mol in the international system).

As a reminder, a mole of a chemical element is the amount of substance containing `6,02214076*10^23` of elementary entities of that element (atoms, molecules, elemental particle, etc.). This number corresponds to the number of Avogadro `N_A`.

`N_A = 6,02214076*10^23 mol^(-1)`

Molar mass of an atom

The molar mass of an atom is directly read in the periodic table.

Molar mass of a molecule

The molar mass of a molecule is equal to the weighted sum of the molar masse of the atoms that compose it. Example: how to calculate the molar mass of the Carbon dioxide molecule ?

The Carbon dioxide molecule `CO_2` contains 1 carbon atom and 2 oxygen atoms:

According to the periodic table, we have (rounded to the nearest gram):

`M_C` = 12 g/mol
`M_O` = 16 g/mol

`M_(CO_2) = M_C + 2 * M_O` = 44 g/mol

See also

Mole calculator
Conversion of molar mass units
Conversion of units of amount of substance
Atoms and Molecular Calculators
Chemistry Calculators