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Chemistry / Stoichiometry

Moles to Grams Converter

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Result

45.0375 g H₂O

m=n×M=2.5 mol×18.015 g/mol=45.0375 gm = n \times M = 2.5\,\text{mol} \times 18.015\,\text{g/mol} = 45.0375\,\text{g}
N=n×NA=1.5055×1024 formula unitsN = n \times N_A = 1.5055 \times 10^{24}\ \text{formula units}

Molar mass M of H₂O: 18.015 g/mol, from standard atomic weights.

Convert between moles and grams for any substance by its chemical formula, using the molar mass from standard atomic weights, and see the number of molecules or formula units the amount contains.

Formula

m=n×M\text{m} = \text{n} \times \text{M}
n=m÷M\text{n} = \text{m} \div \text{M}
N=n×Na,Na=6.02214076×1023per mol\text{N} = \text{n} \times \text{N}_{\text{a}}, \text{N}_{\text{a}} = 6.02214076 \times 10^{23} \text{per mol}

Worked Example

SubstanceH₂O
Amount2.5 mol
Result
Mass45.04 g
Molecules1.5055 × 10²⁴

Water's molar mass is 18.015 g/mol, so 2.5 mol weighs 2.5 × 18.015 = 45.04 g. Multiplying by Avogadro's number gives 2.5 × 6.022 × 10²³ = 1.506 × 10²⁴ molecules.

Frequently Asked Questions

How do you convert grams to moles?

Divide the mass by the molar mass: n = m ÷ M. 100 g of calcium carbonate (CaCO₃, 100.09 g/mol) is 0.999 mol.

What is Avogadro's number?

The number of particles in one mole, exactly 6.02214076 × 10²³ since the 2019 redefinition of the SI. A mole of any substance contains that many atoms, molecules or formula units.

Why do I need the formula and not just the element?

Because the molar mass depends on every atom in the compound. One mole of O₂ weighs 31.998 g while one mole of O atoms weighs 15.999 g, so writing O₂ or O changes the answer by a factor of two.

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