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Molecular weight of gas calculator

Use this calculator to calculate the molecular weight of gas.
To obtain the result, enter the appropriate data.

Molecular weight of gas





Molecular weight of gas

Molecular weight, often confused with molar mass

The molecular weight unit in the SI system is kg. However, much more commonly the molecular weight is expressed in atomic mass units „u” (equal to 1/12 of the atomic mass of the carbon isotope 12C) or „Da” (dalton).

In practice, due to technical difficulties in expressing actual molecular weights, the so-called relative molecular masses - which are calculated as the sum of the relative atomic masses of the atoms that make up it. Relative molecular mass is a dimensionless quantity which should be understood as a multiple of 1/12 of the atomic mass of the carbon isotope 12C.

In the case of populations of molecules with different molecular weights (e.g., polymers, gas mixtures, etc.), the concept of average molecular weight (also called molar) is used. The average molar mass can be calculated as the arithmetic mean or geometric mean weight of individual molecules in the population.

The gas molecular mass can be determined using the formula::
$$ M_{m} = V \cdot 0.0821 \cdot p \cdot \frac{G}{T} $$
\( V \) – gas volume,
\( p \) – gas pressure,
\( G \) – gas mass,
\( T \) – gas temperature,

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