Mole Definition in Chemistry

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By
Anne Marie Helmenstine, Ph.D.
Chemistry Expert
  • Ph.D., Biomedical Sciences, University of Tennessee at Knoxville
  • B.A., Physics and Mathematics, Hastings College
Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels.
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Anne Marie Helmenstine, Ph.D.
Updated July 03, 2019

A Mole is defined as a chemical unit, defined to be 6.022 x 1023 (Avogadro's Constant) entities. In science, this is usually molecules or atoms. The mass of a mole is the gram formula mass of a substance.

Examples:

  • 1 mole of NH3 has 6.022 x 1023 molecules and weighs about 17 grams (Nitrogen's molecular weight is 14 and Hydrogen is 1, 14 + 3 = 17).
  • 1 mole of copper has 6.022 x 1023 atoms and weighs about 63.54 grams.
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Helmenstine, Anne Marie, Ph.D. "Mole Definition in Chemistry." ThoughtCo, Aug. 28, 2020, thoughtco.com/mole-definition-in-chemistry-606377. Helmenstine, Anne Marie, Ph.D. (2020, August 28). Mole Definition in Chemistry. Retrieved from https://www.thoughtco.com/mole-definition-in-chemistry-606377 Helmenstine, Anne Marie, Ph.D. "Mole Definition in Chemistry." ThoughtCo. https://www.thoughtco.com/mole-definition-in-chemistry-606377 (accessed May 7, 2021).