What is the molecular weight of mg3n2

The Molar mass (Formula symbol M.), is the quotient of the mass of a substance and the amount of substance of this substance. The unit is grams per mole (unit symbol: g / mol) or often also kilograms per kilomole (unit symbol: kg / kmol). As with all molar quantities, in which one refers to the base quantity of substance, the underlying particles of the substance must be precisely specified, ideally by giving a formula. For example, one has to distinguish between the molar mass of a hydrogen atom H and the molar mass of a hydrogen molecule H.2 differentiate, even if one only speaks of “hydrogen” in an imprecise way.

The term that is still used frequently molar mass should not be used as it is even stronger than the designation Molar mass leads to the belief that these terms refer to a crowd. But this is not the case, since it is a matter of a material constant of a substance.

The names used in the past Atomic weight, Molecular weight or. Molecular weight should no longer be used. They are out of date and, strictly speaking, also wrong, since a weight is by definition a force (unit: Newton) that is calculated from the product mass * acceleration. The acceleration due to gravity, which is decisive for weights, is also location-dependent.


A mole of a substance is the amount of substance that consists of as many particles as there are twelve grams of the carbon isotope12C. 12C atoms are included. This particle number is about 6.022 x 10 623; it is identical to the numerical value of Avogadro's constant (NA.) in the unit mol−1.

The individual symbols represent the following values:

In physics, the Avogadro constant is occasionally also using the unit kmol−1 than 6.022 x 1026 kmol−1 written; then there are handy numerical values ​​for the mass in the SI base unit of kilograms. Example:

  • 6,022·102312C atoms have a mass of 12 g
  • 6,022·102612C atoms have a mass of 12 kg

Calculation of molar masses

The molar mass of a compound can be calculated if you know its empirical formula: For each element, you can take the stoichiometric coefficient from the total formula - it appears in the total formula after the element symbol. For each element you have to take the molar mass, e.g. from tables - its numerical value is equal to the relative atomic mass. Then the molar mass is obtained as the sum of the molar masses of the elements that make up the connection:

The molar mass of a compound is equal to the sum of the molar masses of the elements multiplied by their stoichiometric coefficients.

Example: water (H2O)


The molar masses of all compounds can be calculated from the molar masses of the chemical elements.

See also

Categories: Chemical Quantity | Atomic physics | thermodynamics