The definition of what a mole is changed the world of chemistry. The moles allow to go from a level of molecules to more manageable units through weight, or what is the same, any chemist can know how many atoms and molecules a sample contains simply by weighing it. How?
Basically one mole of any substance is a weight equal to the molecular weight expressed in atomic mass units. This implies that one mole of any substance contains exactly the same number of molecules .
All the elements of the periodic table have a certain atomic mass. For example, hydrogen has an atomic mass of 1.0079, while oxygen has an atomic mass of 15,999. In this way, a molecule of water (H2O, two atoms of hydrogen linked to one of oxygen) will have an approximate atomic mass of 18. Or what is the same, a mole of water will weigh approximately 18 grams. Similarly, one mole of neon atoms will weigh 20,180 grams. But how can you know how many molecules exist in these 18 grams of pure water, that is, in one mole of water?
Amadeo Avogadro discovered in the early nineteenth century the relationship between the number of molecules or atoms of a substance and the moles. In general, a mole of any substance contains 6.022 x 10 23 molecules or atoms of that substance. Thus, in a mole of water (H2O) there are 6.022 × 10 23 molecules of H2O, or what is the same, 2 × 6.022 × 10 23 hydrogen atoms and 6.022 × 10 23 oxygen atoms.
Mol’s Day is celebrated every year on October 23 in the United States between 6:02 in the morning and 6:02 in the afternoon, taking advantage of the digits of Avogadro’s number.
Unit of measurement
A mole is simply a unit of measurement. Units are invented when existing units are inadequate. Chemical reactions often take place at levels where using grams would not make sense, but using absolute numbers of atoms / molecules / ions would also be confusing.
Like all units, a mole must be based on something reproducible . For example: a mole is the amount of anything that has the same number of particles found in 12,000 grams of carbon-12. That number of particles is Avogadro’s number, which is approximately 6.02×1023. One mole of carbon atoms is 6.02×1023 carbon atoms. Basically, that’s why this particular unit was invented.
Why don’t we just limit ourselves to units like grams (and nanograms and kilograms, etc.)? The answer is that moles give us a consistent method of converting between atoms / molecules and grams. It is simply a convenient unit to use when performing calculations. It may not be too convenient for us if we are learning how to use it for the first time, but once we become familiar with moles, it will be as normal a unit as when we use a dozen or a byte.
Be that as it may, on the Internet we also have converters from grams to moles, for example, in case of a chemical emergency.
