Avogadro Number
Number of particles in one mole.
Formula
Variables
Example
One mole of atoms
How it works
Avogadro’s number tells you how many microscopic particles are counted as 1 mole: atoms, molecules, ions, or other entities. The value 6.022×10^23 comes from measuring and defining the amount of substance so chemists can connect tiny-scale particles to masses we can weigh in the lab. It works because a mole is a counting unit, just like a dozen, but for incredibly large numbers of particles.
When to use it
Use this when converting between moles and number of particles in chemistry problems. It is especially useful for counting molecules in a sample, finding how many ions are present in a given amount of substance, or turning a particle count into moles.
Worked example, step by step
How many molecules are in 3.5 mol of CO2? Step 1: Use the formula N = n × N_A Step 2: Substitute the values N = 3.5 × 6.022×10^23 Step 3: Multiply N = 2.1077×10^24 Step 4: Round appropriately N ≈ 2.1×10^24 molecules of CO2
Common mistakes to avoid
- Using Avogadro’s number as a mass instead of a count
- Forgetting that it applies to any particle type, not just atoms
- Mixing up the mole value with the particle count and not multiplying by 6.022×10^23
Did You Know?
Avogadro's number is so vast that a mole of water drops would cover all Earth's land kilometres deep.
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