# Avogadros Number

Uploaded by masone4718 on Nov 28, 2004

Avogadros number is the number 6.0221367 x 10^23, commonly rounded to just three significant digits: 6.02 x 10^23, and is the number of representative particles in a mole. Avogadro’s number is commonly used to compute the quantities of substances involved in chemical reactions, called stoichiometry, and is one of the most important and versatile components of modern chemistry.

Avogadro’s number is named after the Italian physicist Amadeo Avogadro. Avogadro’s number first came about when Amadeo Avogadro proposed Avogadro’s law in 1811. Avogadro’s law states that under the same conditions of temperature and pressure, equal volumes of different gases contain an equal amount of molecules. The specific number of molecules in one gram-mole of a substance is the value 6.02 x 10^23. For example, the molecular weight of oxygen is 32, so one gram-mole of oxygen has a mass of 32 grams and contains 6.02 x 10^23 molecules (Blauch).

Avogadro’s number also deals with the mole. The mole is a SI unit used to measure the amount of a substance, and is equal to Avogadro’s number. It is equal to the number of carbon atoms in exactly 12 grams of carbon-12. A mole of any substance contains 6.022127 x 10^23 representative particles. A representative particle is any type of particle, such as atoms, molecules, formula units, electrons or ions, and 1 mole of any substance always contains the same number of molecules. Avogadro’s number relates the mass of a mole of a substance to the mass of a single molecule. For example, to find the mass of one molecule of H2O, you would use the formula:

( Mass ) / (Avogadro’s number )

Since the molecular mass of H2O is 18, then to formula would be:

( 18g ) / ( 6.02 x 10^23 )

By using this formula you discover that the mass of one molecule 2.99 x 10^-23 grams (Dickson 106).

A major use of the mole is stoichiometry. The word ‘stoichiometry’ derives from two Greek words: stoicheion (meaning "element") and metron (meaning "measure"). Stoichiometry deals with calculations of the masses of reactants and products in a chemical reaction, and is a very mathematical part of chemistry. You can use stoichiometry...

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Uploaded by: masone4718

Date: 11/28/2004

Category: Chemistry

Length: 5 pages (1,128 words)

Views: 3350

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