15.1 The mole

Amount of substance n is measured in moles, allowing microscopic entities to be counted through a macroscopic quantity.

Name the entities being counted—atoms, molecules, ions or formula units—before converting between mass, moles and particles.

One mole of water means one mole of H₂O molecules, not one mole of hydrogen atoms alone.

Moles are not a mass unit; different substances have different masses per mole.

One mole contains N_A≈6.02×10²³ specified particles or entities. The number is a count, not a mass.

Multiply moles by N_A to find particles, or divide particle count by N_A to find amount. State whether entities are atoms, molecules or ions.

0.50 mol of electrons contains about 3.01×10²³ electrons; 1 mol of NaCl contains that many formula units.

Avogadro’s constant is not the number of grams in a mole and does not change with substance.