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In 1811, Amedeo Avogadro theorized that "equal volumes of all gases at the same temperature and pressure contain the same number of molecules." Today, this is known as Avogadro's Law. Experiments based on this principle eventually led to the calculation of the number of molecules in one cubic centimeter of gas. This number of molecules was determined to be roughly 6.02 x 1023; this was dubbed "Avogadro's number." What's it good for? It helps us define the mole. What's a mole? We found the official definition on ChemTeam's page on The Mole and Molar Mass: "The mole is the amount of substance of a system which contains as many elementary
entities as there are atoms in 0.012 kilogram of carbon-12." The number of atoms in 0.012 kg of carbon-12 is 6.0221367 x 1023 -- named Avogadro's number. Put simply, one mole of any substance contains Avogadro's number of molecules, atoms, or "elementary entities" of that substance: - One mole of oxygen contains 6.0221367 x 1023 atoms of oxygen.
- One mole of water contains 6.0221367 x 1023 molecules of water.
- One mole of gorillas contains 6.0221367 x 1023 gorillas.
Avogadro's number is commonly used to compute the results of chemical reactions. It allows chemists to determine the exact amounts of substances produced in a given reaction. This is called stoichiometry. Homework: Use Avogadro's number and the Periodic Table of Rejected Elements to figure out how many molecules there are in 10 grams of Tedium!
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