Molar mass of sodium tetraborate (Na₂B₄O₇)

The molar mass of sodium tetraborate (Na₂B₄O₇) is 201.212539 g/mol, summed from the IUPAC standard atomic weights of Na x 2, B x 4, O x 7. Anhydrous borax.

Mass of sample

Amount of substance

mol

Molar mass

201.212 539g/mol

= Exact Molar mass of sodium tetraborate

Moles in the sample mass: 0.049 698 692 mol
Mass of that amount of substance: 201.212 54
Molecules in the sample mass: 2.99293e+22

Show the working

Mass of sample = 10
Amount of substance = 1
Molar mass = 22.98976928*2 + 10.81*4 + 15.999*7 = 201.213
Moles in the sample mass = 10 / 201.213 = 0.049 698 7
Mass of that amount of substance = 1 * 201.213 = 201.213
Molecules in the sample mass = 0.049 698 7 * NA = 2.99293e+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.

Scenarios & local history

Compare a saved scenario

Recent calculations

The formula

Molar mass = sum over elements of (atomic weight x number of atoms)
For Na₂B₄O₇: 22.98976928 x 2 + 10.81 x 4 + 15.999 x 7 = 201.212539 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.

Anhydrous borax.

Composition by mass

Element	Atoms	Atomic weight	Contribution (g/mol)	Share of mass
Oxygen (O)	7	15.999	111.993	55.659 %
Sodium (Na)	2	22.98976928	45.979539	22.851 %
Boron (B)	4	10.81	43.24	21.49 %

Contributions add to the molar mass of 201.212539 g/mol. Atomic weights are the IUPAC 2021 standard values.

Frequently asked

What is the molar mass of sodium tetraborate?

201.212539 g/mol, for the formula Na₂B₄O₇.

How do you convert grams of sodium tetraborate to moles?

Divide the mass in grams by 201.212539 g/mol. One gram of sodium tetraborate is 0.00496987 mol.

How many grams are in one mole of sodium tetraborate?

201.212539 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.