Chemistry / Unit 3 Chem 0379 worked example, 60 to 90 seconds
Converting Moles to Number of Entities
The idea
Converting a mole amount to a count of entities means multiplying the mole amount by Avogadro's number, letting the mole units cancel against the per-mole unit carried by the constant itself.
In practice
A sample of potassium contains 0.12 mol of atoms. Multiplying 0.12 mol by 6.02214076×10^23 per mole gives roughly 7.2×10^22 potassium atoms in that sample. Chained with the mass-to-mole step at Chem 0376, a measured mass of any substance can be carried all the way to a literal atom count in two short multiplication-and-division steps, one after the other. The same chain works in reverse: dividing a known entity count by Avogadro's number recovers the mole amount that produced it, which then converts back to mass.
Where people slip
Skipping straight from mass to particle count without stopping at moles hides the unit cancellation that makes the calculation trustworthy, and it invites errors a mole-amount checkpoint would otherwise catch.
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