Mole

High School

Definition

The SI unit for the amount of a substance, defined as the number of particles equal to about 6.022 × 10²³ (Avogadro's number). The mole allows chemists to count atoms and molecules by weighing, linking the mass of a substance to the number of particles it contains.

Worked examples

\(1 \) mole of \( \)H\(_2\)O\( = 6.022 \times 10^{23} \) water molecules\(\)

One mole of any substance always contains Avogadro's number of particles.

\(12.00 \) g C\( \times \frac{1 \) mol\(}{12.01 \) g\(} \approx 1.00 \) mol C\(\)

Dividing mass by molar mass gives the number of moles, letting you count atoms by weighing.

Common mistakes

\(1 \) mole\( = 1 \) gram\(\) → \(1 \) mole\( = 6.022 \times 10^{23} \) particles\(\) The mole counts particles, not mass; different substances have different molar masses.
\(6.022 \times 10^{23} \) atoms of C\( = 6.022 \times 10^{23} \) g\(\) → \(6.022 \times 10^{23} \) atoms of C\( = 12.01 \) g\(\) One mole of carbon atoms has a mass of 12.01 g, the molar mass of carbon.
Avogadro's number only applies to atoms, not molecules → Avogadro's number applies to any particles: atoms, molecules, ions, or formula units A mole counts any type of particle, not just atoms.

Where you'll use it next

You'll use the mole in stoichiometry to balance chemical equations and predict reaction yields, in solution chemistry to calculate molarity, and in gas laws to relate volume and particle count.

Found in 1 StudyPug lesson

Moles, Mass & Gas Calculations in Stoichiometry

Chemistry 11

Unlock the power of stoichiometry! Learn to calculate moles, mass, and gas quantities in chemical reactions. Master these fundamental concepts for success in chemistry and beyond.

11th Grade11th