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Chemicals in Biology
Brownian Motion

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Moles and Avogadro's Number

A mole is 6.02 x 1023 basic units of a substance. The basic unit is usually considered to be an atom or a molecule (for example, carbon or water)1. It is also often called the chemical amount. The word mole comes from the Latin and means "massive heap". It is one of the fundamental measures developed as part of the International System of Weights and Measures.

The number of basic units in the mole is based on Avogadro's number, 6.02 x 1023. This is scientific notation for a very big number: 602,214,199,000,000,000,000,000 or about 602 sextillion. Avegadro's number is determined by figuring out how many carbon atoms it takes to equal 12 grams in weight2.

The molar weight of a substance, then, is the number of grams one mole of the substance weighs. This is equivalent to the atomic weight and can be read on any chemical chart. This is a convenient way of comparing different substances in chemistry and can be useful in determining how much of a substance will be necessary when combining elements to create molecules.

Believe it or not, there is a "National Mole Day". It is set aside to help foster interest in chemistry. It happens on the 23rd of October every year between 6.02 a.m and 6.02 p.m.3


  1. What is a Mole?
  2. Mole Concept
  3. Mole Day


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