Mole Day celebrated everyear on October 23 from 6:02 a.m. - 6:02 p.m

Celebrating Mole Day to foster interest in chemistry

Mole Day

Mole Day celebrated annually on October 23 from 6:02 a.m. to 6:02 p.m. commemorates Avogadro’s Number (6.02 x 1023), which is a basic measuring unit in chemistry. Mole Day was created as a way to foster interest in chemistry. Schools throughout the United States and around the world celebrate Mole Day with various activities related to chemistry and/or moles.

What is a mole?

For a given molecule, one mole is a mass (in grams) whose number is equal to the molar mass of the molecule. For example, the water molecule has an molar mass of 18, therefore one mole of water weighs 18 grams. Similarly, a mole of neon has a molar mass of 20 grams. In general, one mole of any substance contains Avogadro’s Number of molecules or atoms of that substance. This relationship was first discovered by Amadeo Avogadro (1776-1858) and he received credit for this after his death.

Avogadro’s Number

Avogadro’s number is the number of particles found in one mole of a substance. It is the number of atoms in exactly 12 grams of carbon-12. This experimentally determined value is approximately 6.0221 x 1023 particles per mole. It is also known as Avogadro’s constant.


Avogadro’s contributions to chemistry

The Italian scientist, Amedeo Avogadro is most famous for his contributions to theory of moles and molecular weight, including what is known as Avogadro’s law. In respect of his contributions to the molecular theory, the number of molecules in one mole was renamed Avogadro’s number.

In 1811 Avogadro theorized that equal volumes of gases at the same temperature and pressure contain equal numbers of molecules. He further established that relative molecular weights of any two gases are similar to the ratio of the densities of the two gases under the constant conditions of temperature and pressure. His suggestion is now known as the Avogadro’s principle. He also cleverly reasoned that simple gases were not formed of solitary atoms but were instead compound molecules of two or more atoms. (Avogadro did not actually use the word atom; at the time the words atom and molecule were used almost interchangeably. He talked about three kinds of “molecules,” including an “elementary molecule”- what we would call an atom). Thus Avogadro was able to resolve the confusion that Dalton and others had encountered regarding atoms and molecules at that time.

Avogadro’s findings were almost completely neglected until it was forcefully presented by Stanislao Cannizarro at the Karlsruhe Conference in 1860. He demonstrated that Avogadro’s Principle was not only helpful to determine molar masses, but also, indirectly, atomic masses. Avogadro’s work was mainly rejected before due to earlier established conviction that chemical combination occurred due to the similarity between unlike elements. After the electrical discoveries of Galvani and Volta, this similarity was in general attributed to the attraction between unlike charges.

The number of molecules in one mole is now called Avogadro’s number taking the value of 6.0221367 x 1023. The number was not actually determined by Avogadro himself. It was given his name due to his outstanding contribution to the development of molecular theory.

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