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Daily Dose of Utilities

Grams to Moles Calculator (Moles, Mass and Particles)

To convert grams to moles, divide the mass by the molar mass. 36 g of water is 36 ÷ 18.015 g/mol ≈ 2.00 mol, and multiplying by Avogadro's number gives about 1.20 × 10²⁴ molecules.

g

Mass

36 g

Moles

1.9983 mol

H₂O particles

1.203 × 10²⁴

Molar mass

18.015 g/mol

Atoms in total

3.61 × 10²⁴

Show the math

  1. 1

    Molar mass of H₂O

    2 × 1.008 + 15.999 = 18.015 g/mol

    The mass of one mole, from the atomic masses on the periodic table.

    = 18.015 g/mol

Read the steps as text
  1. Molar mass of H₂O. 2 × 1.008 + 15.999 = 18.015 g/mol The mass of one mole, from the atomic masses on the periodic table.
  2. Grams to moles: divide by the molar mass. 36 g ÷ 18.015 g/mol = 1.9983 mol
  3. Moles to particles: multiply by Avogadro's number. 1.9983 mol × 6.022 × 10²³ /mol = 1.203 × 10²⁴
  4. Count the individual atoms. 1.203 × 10²⁴ × 3 atoms each = 3.61 × 10²⁴ atoms Each H₂O unit contains 3 atoms.

The mole connects mass and particle count

A mole is a fixed number of particles: exactly 6.02214076 × 10²³, known as Avogadro's number. Chemists use it because atoms are far too small to count, but a mole of any substance has a mass in grams equal to its molar mass, which you can work out from the periodic table.

That gives two simple conversions. Grams to moles: divide by the molar mass. Moles to particles: multiply by Avogadro's number. Going the other way, you multiply by the molar mass or divide by Avogadro's number. This calculator does both from whichever quantity you know.

Molecules versus atoms

The particle count is the number of molecules (or formula units, for an ionic compound like NaCl). Each of those contains several atoms, so the calculator also multiplies by the atoms in one unit. A mole of water is 6.022 × 10²³ molecules, but 3 times as many atoms, because each molecule has two hydrogens and one oxygen.

To type a very large particle count, use e notation: 1.5e24 means 1.5 × 10²⁴. Results that are very large or very small are shown in scientific notation too.

Frequently asked questions

How do I convert grams to moles?
Divide the mass in grams by the substance's molar mass in g/mol. For 10 g of sodium chloride (58.44 g/mol), that's 10 ÷ 58.44 = 0.171 mol.
How do I convert moles to grams?
Multiply the number of moles by the molar mass. 0.5 mol of carbon dioxide (44.009 g/mol) weighs 0.5 × 44.009 = 22.0 g.
What is Avogadro's number?
6.02214076 × 10²³, the number of particles in one mole. Since 2019 it has been an exact defined value rather than a measurement.
How many molecules are in a gram of water?
About 3.34 × 10²². One gram is 1 ÷ 18.015 = 0.0555 mol, and 0.0555 × 6.022 × 10²³ ≈ 3.34 × 10²² molecules.

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