Why Use 4 Significant Figures for Avogadro’s Number?


Although Avogadro's Number is named for Avogadro, he did not invent or discover it.

Although Avogadro’s Number is named for Avogadro, he did not invent or discover it.

Avogadro’s number (Avogadro’s constant) is the quantity of objects found in 1 mole of a sample. It is the number of atoms in exactly 12 grams of carbon-12. The value is determined experimentally, so there is error in Avogadro’s number, as with any measurement.

So, while we have a good idea of what Avogadro’s number is, it’s not an exact number. You can express it as 6.02214179(30)×1023. However, for most chemistry calculations, you will be working with atomic masses, which are commonly reported using 4 significant figures.

When you perform calculations using significant figures, you use the smallest number of significant digits. So, if you are using a mass of carbon that is 12.01 grams/mole (4 significant figures), you would use 6.022 x 1023 as Avogadro’s number (4 significant figures).

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.