Chemistry·Stoichiometry · NSSCO 4.1
The mole concept
Narrated lesson · press play
Atoms are far too small and too many to count — so chemists count them in moles. Learn what relative atomic mass and relative formula mass mean, what the Avogadro constant is, how one mole weighs the relative mass in grams, and how we measure concentration.
What you'll learn in this lesson
By the end you should be able to (NSSCO Chemistry 4.1):
- Define relative atomic mass Ar as the ratio of the average mass of the atoms of an element to 1/12 the mass of a carbon-12 atom
- Define relative formula mass Mr as the sum of the relative atomic masses of all atoms in a molecule or compound
- State that a mole is an amount of substance containing approximately 6.022 × 10²³ particles
- State that this number (6.022 × 10²³) is the Avogadro constant
- State that one mole of any substance has a mass equal to its relative mass in grams
- State that the empirical formula is the simplest whole-number ratio of the elements in a compound
- Define empirical formula mass as the Mr of a compound in its simplest form
- Define concentration as mass per volume or moles per volume (g/dm³ and mol/dm³)
Loading your lesson…
You're watching a free 3-minute preview — create a free account to keep going.