Mendeleev · Chemistry pathway · level 2
The mole: counting the invisible
The mole links microscopic entities to measurable quantities. One mole contains exactly 6.02214076 × 10²³ elementary entities.
The essential idea
The mole links microscopic entities to measurable quantities. One mole contains exactly 6.02214076 × 10²³ elementary entities.
Example
A mole of water and a mole of iron contain the same number of entities, but not the same mass.
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Mini problem
How many entities are in 0.5 mol?
Show the solution
0.5 × 6.02214076 × 10²³ ≈ 3.011 × 10²³ entities.
Common mistake
Do not replace reasoning with a memorized rule. Always check geometry, units, coefficients or model assumptions.
Guided exercise
How many molecules are in 2.00 mol of water?
Show the detailed solution
N = n × Nₐ = 2.00 × 6.02214076 × 10²³ ≈ 1.204 × 10²⁴ molecules.
Avoid this
Always state what is being counted: molecules, atoms, ions or another entity.