What is Avogadro's number?

• A. 6.02x10^24
• B. 6.02x10^23
• C. 6.02x10^22
• D. 6.02x10^25

Answer: (B)

Avogadro's number is the number of elementary entities in one mole of a substance. It’s the bridge between counting particles and measuring amount: one mole contains 6.02×10^23 particles, whether they’re atoms, molecules, or ions, depending on the substance.

This lets you go from a count of particles to moles (and vice versa): if you have 6.02×10^23 particles, that’s one mole; if you have twice that many, you have two moles, and so on. The one-mole quantity corresponds to 12 grams of carbon-12 by definition, which sets the scale for all substances.

So the value you use is 6.02×10^23 particles per mole. Choices with powers of 10 that are 10× or 0.1× or 10^24, 10^22, etc., reflect other multiples (like ten moles, one-tenth of a mole, etc.), but for a single mole, the correct figure is 6.02×10^23.