Mole Calculator
Number of Moles
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Number of Molecules
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(Note: molecules, not atoms)
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How to Calculate Moles
A mole is a counting unit for atoms and molecules: 1 mole = 6.022 × 10²³ particles (Avogadro's number). To find the number of moles, divide the mass by the molar mass: n = m / M, where m is mass in grams and M is molar mass in g/mol.
Molar mass is the mass of one mole of a substance and equals its molecular weight in g/mol. For example, water (H₂O) has a molar mass of about 18.015 g/mol. So 18 grams of water contains approximately 1 mole (6.022 × 10²³ molecules).
Mole calculations are fundamental to chemistry — they're used in stoichiometry, solution preparation, and reaction yield calculations. The mole bridges the gap between the atomic scale and the macroscopic scale we can measure in the laboratory.
Frequently Asked Questions
What is a mole in chemistry?
A mole is 6.022 × 10²³ particles (Avogadro's number). It's the amount of substance containing as many entities as there are atoms in 12 grams of carbon-12.
How do you calculate moles from grams?
Moles = mass (g) / molar mass (g/mol). For 36 grams of water (M = 18 g/mol): 36/18 = 2 moles.
What is Avogadro's number?
6.022 × 10²³ — the number of particles in one mole. It's an incredibly large number, reflecting how tiny atoms and molecules are.
What is the difference between moles and molecules?
A mole is a counting unit (like a dozen = 12). Number of molecules = moles × Avogadro's number.