Molar mass of sodium metabisulfite (Na₂S₂O₅)

The molar mass of sodium metabisulfite (Na₂S₂O₅) is 190.094539 g/mol, summed from the IUPAC standard atomic weights of Na x 2, S x 2, O x 5.

Mass of sample

Amount of substance

mol

Molar mass

190.094 539g/mol

= Exact Molar mass of sodium metabisulfite

Moles in the sample mass: 0.052 605 404 mol
Mass of that amount of substance: 190.094 54
Molecules in the sample mass: 3.16797e+22

Show the working

Mass of sample = 10
Amount of substance = 1
Molar mass = 22.98976928*2 + 32.06*2 + 15.999*5 = 190.095
Moles in the sample mass = 10 / 190.095 = 0.052 605 4
Mass of that amount of substance = 1 * 190.095 = 190.095
Molecules in the sample mass = 0.052 605 4 * NA = 3.16797e+22

Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.

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The formula

Molar mass = sum over elements of (atomic weight x number of atoms)
For Na₂S₂O₅: 22.98976928 x 2 + 32.06 x 2 + 15.999 x 5 = 190.094539 g/mol
Moles = mass / molar mass; mass = moles x molar mass
Molecules = moles x 6.02214076 x 10^23 (the Avogadro constant, exact by definition)

Molar mass in grams per mole is numerically equal to the molecular mass in daltons, so this figure doubles as the molecular weight.

Atomic weights are the IUPAC 2021 standard values. Several elements have a range rather than a single value because isotope ratios vary between sources; the conventional single value is used here.

Composition by mass

Element	Atoms	Atomic weight	Contribution (g/mol)	Share of mass
Oxygen (O)	5	15.999	79.995	42.082 %
Sulfur (S)	2	32.06	64.12	33.731 %
Sodium (Na)	2	22.98976928	45.979539	24.188 %

Contributions add to the molar mass of 190.094539 g/mol. Atomic weights are the IUPAC 2021 standard values.

Frequently asked

What is the molar mass of sodium metabisulfite?

190.094539 g/mol, for the formula Na₂S₂O₅.

How do you convert grams of sodium metabisulfite to moles?

Divide the mass in grams by 190.094539 g/mol. One gram of sodium metabisulfite is 0.00526054 mol.

How many grams are in one mole of sodium metabisulfite?

190.094539 g, by definition of the molar mass.

Is molar mass the same as molecular weight?

Numerically yes, for the purposes of this calculation. Molecular weight is a dimensionless ratio and molar mass carries units of g/mol, but the digits are identical.

Where the numbers come from

IUPAC 2021 standard atomic weights; Avogadro constant fixed by the 2019 SI.