Tutoring high school chemistry, the concept of a mole is paramount.  The tutor offers this light introduction to pave the way for more….

Phrases you might overhear from high school chemistry are “molar mass” or “How many atoms in a mole of water?” To non-chemists, these ideas might need clarification.

A mole is 6.02 x 10²³ particles. The number 6.02 x 10²³ is known as Avogadro’s number, in honor of the chemist who focused on the numbers of molecules that react during chemical processes between gases. Some people just call 6.02×10²³ the molar number.

In practical terms, Avogadro’s number is the number of atoms that, for each element, yields the mass in grams that you see on the periodic table. The masses are the decimal numbers. For instance, if you look at carbon, you’ll see its mass is 12.0. This means that the mass of one mole of carbon atoms – aka, its molar mass – is 12.0 grams. One mole of carbon atoms is, of course, 6.02×10²³ atoms of carbon.

One mole of water – which is, of course, H₂O – contains two moles of hydrogen (H) and one of oxygen (O). The total atom count is 3 moles, or 3(6.02×10²³) = 1.81×10²⁴ atoms.

In our everyday life, we have our convenient quantities of things – a dozen, for instance. Chemists have their own convenient numbers, one of which is 6.02×10²³, the molar number. It’s an inescapable concept for high school chemistry students:)

Source: Mortimer, Charles E. Chemistry. Belmont, California: Wadsworth, 1986.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.