[XM8]

Ok we're learning about this mole unity and I don't understand it.

We're always diving some number by 6,02 x 10^23

What does that number mean? It's something to do with carbon right?

Where do the numbers we divide come from? Like molecules in an atom of oxygen? Where am I supposed to get those from?


If anyone could please try and explain this in detail I'd greatly appreciate it,


Thanks,

-Xm8

[Perito]

The number, 6,023 x 10^23 is called "Avogadro's number". It's a very important number to a chemist. It is defined as the number of molecules (or atoms if the substance is composed of only one atom) in "1 gram mole" of any substance. Usually, we simply call a "gram mole" a "mole" of the substance.

1 gram mole of a substance is the weight, in grams, corresponding to the molecular weight or atomic weight (as appropriate) of the substance.

For example, "carbon" (C) has an atomic weight of 12. So, 12 grams of carbon will contain 6,023 x 10^23 atoms of carbon.

Oxygen doesn't exist in air as "O", but as "O2" (2 oxygen atoms bonded together). The atomic weight of oxygen is 16, so the molecular weight of oxygen is 2 x 16 = 32. In 32 grams of oxygen, you will find 6,023 x 10^23 molecules (they're molecules now because the atoms are bonded together).

One more example. Water is H2O -- two atoms of hydrogen and one atom of oxygen bonded. The hydrogen atoms are bonded to the oxygen atom. Hydrogen has an atomic weight of 1. Oxygen has an atomic weight of 16 so H2O has a molecular weight of 1 + 1 + 16 = 18. In 18 grams of water, you will find 6,023 x 10^23 molecules of water.