Molar mass of copper(ii) sulfate pentahydrate (CuSO₄·5H₂O)

The molar mass of copper(ii) sulfate pentahydrate (CuSO₄·5H₂O) is 249.677 g/mol, summed from the IUPAC standard atomic weights of Cu, S, O x 9, H x 10. The familiar blue crystals.

Mass of sample

Amount of substance

mol

Molar mass

249.677g/mol

= Exact Molar mass of copper(ii) sulfate pentahydrate

Moles in the sample mass: 0.040 051 747 mol
Mass of that amount of substance: 249.677
Molecules in the sample mass: 2.41197e+22

Show the working

Mass of sample = 10
Amount of substance = 1
Molar mass = 63.546 + 32.06 + 15.999*9 + 1.008*10 = 249.677
Moles in the sample mass = 10 / 249.677 = 0.040 051 7
Mass of that amount of substance = 1 * 249.677 = 249.677
Molecules in the sample mass = 0.040 051 7 * NA = 2.41197e+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 CuSO₄·5H₂O: 63.546 + 32.06 + 15.999 x 9 + 1.008 x 10 = 249.677 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.

The familiar blue crystals.

Composition by mass

Element	Atoms	Atomic weight	Contribution (g/mol)	Share of mass
Oxygen (O)	9	15.999	143.991	57.671 %
Copper (Cu)	1	63.546	63.546	25.451 %
Sulfur (S)	1	32.06	32.06	12.841 %
Hydrogen (H)	10	1.008	10.08	4.0372 %

Contributions add to the molar mass of 249.677 g/mol. Atomic weights are the IUPAC 2021 standard values.

Frequently asked

What is the molar mass of copper(ii) sulfate pentahydrate?

249.677 g/mol, for the formula CuSO₄·5H₂O.

How do you convert grams of copper(ii) sulfate pentahydrate to moles?

Divide the mass in grams by 249.677 g/mol. One gram of copper(ii) sulfate pentahydrate is 0.00400517 mol.

How many grams are in one mole of copper(ii) sulfate pentahydrate?

249.677 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.