Molar mass of dimethyl sulfoxide (C₂H₆OS)

The molar mass of dimethyl sulfoxide (C₂H₆OS) is 78.129 g/mol, summed from the IUPAC standard atomic weights of C x 2, H x 6, O, S.

Mass of sample

Amount of substance

mol

Molar mass

78.129g/mol

= Exact Molar mass of dimethyl sulfoxide

Moles in the sample mass: 0.127 993 45 mol
Mass of that amount of substance: 78.129
Molecules in the sample mass: 7.70795e+22

Show the working

Mass of sample = 10
Amount of substance = 1
Molar mass = 12.011*2 + 1.008*6 + 15.999 + 32.06 = 78.129
Moles in the sample mass = 10 / 78.129 = 0.127 993
Mass of that amount of substance = 1 * 78.129 = 78.129
Molecules in the sample mass = 0.127 993 * NA = 7.70795e+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 C₂H₆OS: 12.011 x 2 + 1.008 x 6 + 15.999 + 32.06 = 78.129 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
Sulfur (S)	1	32.06	32.06	41.035 %
Carbon (C)	2	12.011	24.022	30.747 %
Oxygen (O)	1	15.999	15.999	20.478 %
Hydrogen (H)	6	1.008	6.048	7.741 %

Contributions add to the molar mass of 78.129 g/mol. Atomic weights are the IUPAC 2021 standard values.

Frequently asked

What is the molar mass of dimethyl sulfoxide?

78.129 g/mol, for the formula C₂H₆OS.

How do you convert grams of dimethyl sulfoxide to moles?

Divide the mass in grams by 78.129 g/mol. One gram of dimethyl sulfoxide is 0.0127993 mol.

How many grams are in one mole of dimethyl sulfoxide?

78.129 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.