Molar mass of sodium peroxide (Na₂O₂)

The molar mass of sodium peroxide (Na₂O₂) is 77.9775386 g/mol, summed from the IUPAC standard atomic weights of Na x 2, O x 2.

Mass of sample

Amount of substance

mol

Molar mass

77.977 538 6g/mol

= Exact Molar mass of sodium peroxide

Moles in the sample mass: 0.128 242 06 mol
Mass of that amount of substance: 77.977 539
Molecules in the sample mass: 7.72292e+22

Show the working

Mass of sample = 10
Amount of substance = 1
Molar mass = 22.98976928*2 + 15.999*2 = 77.9775
Moles in the sample mass = 10 / 77.9775 = 0.128 242
Mass of that amount of substance = 1 * 77.9775 = 77.9775
Molecules in the sample mass = 0.128 242 * NA = 7.72292e+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 Na₂O₂: 22.98976928 x 2 + 15.999 x 2 = 77.9775386 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
Sodium (Na)	2	22.98976928	45.979539	58.965 %
Oxygen (O)	2	15.999	31.998	41.035 %

Contributions add to the molar mass of 77.9775386 g/mol. Atomic weights are the IUPAC 2021 standard values.

Frequently asked

What is the molar mass of sodium peroxide?

77.9775386 g/mol, for the formula Na₂O₂.

How do you convert grams of sodium peroxide to moles?

Divide the mass in grams by 77.9775386 g/mol. One gram of sodium peroxide is 0.0128242 mol.

How many grams are in one mole of sodium peroxide?

77.9775386 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.