Graham's Law Definition

Chemistry Glossary Definition of Graham's Law

Thomas Graham
Thomas Graham. Wikimedia Commons/Public Domain
By
Anne Marie Helmenstine, Ph.D.
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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Updated on July 03, 2019

Graham's Law is a relation which states that the rate of the effusion of a gas is inversely proportional to the square root of its density or molecular mass.

Rate1 / Rate2 = (M2 / M1)1/2

Where:
Rate1 is the rate of effusion of one gas, expressed as volume or as moles per unit time.
Rate2 is the rate of effusion of the second gas.
M1 is the molar mass of gas 1.
M2 is the molar mass of gas 2.

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Helmenstine, Anne Marie, Ph.D. "Graham's Law Definition." ThoughtCo, Feb. 16, 2021, thoughtco.com/definition-of-grahams-law-604513. Helmenstine, Anne Marie, Ph.D. (2021, February 16). Graham's Law Definition. Retrieved from https://www.thoughtco.com/definition-of-grahams-law-604513 Helmenstine, Anne Marie, Ph.D. "Graham's Law Definition." ThoughtCo. https://www.thoughtco.com/definition-of-grahams-law-604513 (accessed April 1, 2023).