The Mole Concept (College Board AP Chemistry)

• The number of particles that react in a chemical experiment cannot be directly determined because the size and mass of an individual particle is so small
• Moles are used to relate the mass of a sample to the number of particles it contains
• The mole (mol) is the SI unit for the amount of substance
• The number of moles (n) of a substance and the number of constituent particles or formula units it contains are related by Avogadro’s number (N_A)

N_A = 6.022 x 10²³ mol^-1

Number of constituent particles = N_A x n

 

1 mole of…	Fe atoms	H2O molecules	Al2(SO4)3 formula units
Contains…	6.022 x 1023 Fe atoms	1.2044 x 1024 H atoms 6.022 x 1023 O atoms	1.2044 x 1024 Al3+ ions 1.8066 x 1024 SO42- ions