Which expression converts particles to moles?

• A. Moles × Avogadro's Number
• B. Moles ÷ Avogadro's Number
• C. Grams ÷ Molar Mass
• D. Particles ÷ Avogadro's Number

Answer: (D)

Converting particles to moles uses division by Avogadro's number because one mole contains exactly Avogadro’s number of particles. So to find how many moles are in a given count of particles, you divide by Avogadro’s number. The expression that does this is particles ÷ Avogadro’s Number.

If you multiplied moles by Avogadro’s number, you’d get the total number of particles, not moles. Dividing moles by Avogadro’s number would give a tiny fraction of a mole, not the result from a particle count. And using grams divided by molar mass converts mass to moles, not particle counts. For example, 6.02×10^23 particles divided by 6.02×10^23 equals 1 mole.