Avogadro's law (sometimes referred to as Avogadro's hypothesis or Avogadro's principle) is an experimental gas law relating volume of a gas to the amount of substance of gas present. A modern statement of Avogadro's law is:
Avogadro's law states that, "equal volumes of all gases, at the same temperature and pressure, have the same number of molecules". For a given mass of an ideal gas, the volume and amount (moles) of the gas are directly proportional if the temperature and pressure are constant.
which can be written as:

V \propto n\,
or

\frac{V}{n}=k
where:

V is the volume of the gas

n is the amount of substance of the gas (measured in moles).

k is a constant equal to RT/P, where R is the universal gas constant, T is the Kelvin temperature, and P is the pressure. As temperature and pressure are constant, RT/P is also constant and represented as k. This is derived from the ideal gas law.
This law explains how, under the same condition of temperature and pressure, equal volumes of all gases contain the same number of molecules. For comparing the same substance under two different sets of conditions, the law can be usefully expressed as follows:

\frac{V_1}{n_1} = \frac{V_2}{n_2}
The equation shows that, as the number of moles of gas increases, the volume of the gas also increases in proportion. Similarly, if the number of moles of gas is decreased, then the volume also decreases. Thus, the number of molecules or atoms in a specific volume of ideal gas is independent of their size or the molar mass of the gas.
The law is named after Amedeo Avogadro who, in 1811,^{[1]} hypothesized that two given samples of an ideal gas, of the same volume and at the same temperature and pressure, contain the same number of molecules. As an example, equal volumes of molecular hydrogen and nitrogen contain the same number of molecules when they are at the same temperature and pressure, and observe ideal gas behavior. In practice, real gases show small deviations from the ideal behavior and the law holds only approximately, but is still a useful approximation for scientists.
Mathematical definition
Avogadro's law is stated mathematically as:

\frac{V}{n} = k
Where:

V is the volume of the gas(es).

n is the amount of substance of the gas.

k is a proportionality constant.
The most significant consequence of Avogadro's law is that the ideal gas constant has the same value for all gases. This means that:

\frac{p_1\cdot V_1}{T_1\cdot n_1}=\frac{p_2\cdot V_2}{T_2 \cdot n_2} = constant
Where:

p is the pressure of the gas in the cell

T is the temperature in kelvin of the gas
Ideal gas law
A common rearrangement of this equation is by letting R be the proportionality constant, and rearranging as follows:

pV = nRT
This equation is known as the ideal gas law.
Molar volume
Taking STP to be 101.325 kPa and 273.15 K, we can find the volume of one mole of a gas:

V_{\rm m} = \frac{V}{n} = \frac{RT}{p} = \frac{(8.314 \mathrm{ J} \mathrm{ mol}^{1} \mathrm{ K}^{1})(273.15 \mathrm{ K})}{101 325 \mathrm{ Pa}} = 22.41 \mathrm{ dm}^3 \mathrm{ mol}^{1} = 22.41 \mathrm{ liters}/ \mathrm{ mol}
For 100.00kPa and 273.15 K, the molar volume of an ideal gas is 22.712 dm^{3}mol^{−1}.
See also
References
External links

Avogadro's law at the University of Fribourg

Avogadro's law at the Royal Society of Chemistry
This article was sourced from Creative Commons AttributionShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, EGovernment Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a nonprofit organization.