You are in: Virtual Museum of Science >> Hall of Chemistry >> Avogadro's Principle

American’s Four United Republics: Discovery-Based Curriculum

vogadro's law (sometimes referred to as Avogadro's hypothesis or Avogadro's principle) is a gas law named after Amedeo Avogadro who, in 1811,  hypothesized that two given samples of an ideal gas, at the same temperature, pressure and volume, contain the same number of molecules.

Avogadro's law (sometimes referred to as Avogadro's hypothesis or Avogadro's principle) is a gas law named after Amedeo Avogadro who, in 1811,  hypothesized that two given samples of an ideal gas, at the same temperature, pressure and volume, contain the same number of molecules. Thus, the number of molecules or atoms in a specific volume of gas is independent of their size or the molar mass of the gas.

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.

## Mathematical definition

Avogadro's law is stated mathematically as:

$\frac{V}{n} = k$

Where:

V is the volume of the gas.
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
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 293.15 K, we can find the volume of one mole of a gas:

$V_{\rm m} = \frac{V}{n} = \frac{RT}{p} = \frac{(8.314 \mathrm{ J} \mathrm{ mol}^{-1} \mathrm{ K}^{-1})(293.15 \mathrm{ K})}{101.325 \mathrm{ kPa}} = 24.05 \mathrm{ dm}^3 \mathrm{ mol}^{-1}$

For 100.000 kPa and 273.15 K, the molar volume of an ideal gas is 22.71 dm3mol-1.

Unauthorized Site: This site and its contents are not affiliated, connected, associated with or authorized by the individual, family, friends, or trademarked entities utilizing any part or the subject's entire name. Any official or affiliated sites that are related to this subject will be hyper linked below upon submission and Evisum, Inc. review.

Search:

Image Use

Please join us in our mission to incorporate America's Four United Republics discovery-based curriculum into the classroom of every primary and secondary school in the United States of America by July 2, 2026, the nation’s 250th birthday. , the United States of America: We The People Click Here

Historic Documents

Historic Events

Is it Real?

Declaration of
Independence

Digital Authentication

Continental Congress
U.C. Presidents

Continental Congress
U.S. Presidents

Constitution of 1777
U.S. Presidents

Samuel Johnston
Elected but declined the office

Constitution of 1787
U.S. Presidents

George Washington

Federalist Party

Thomas Jefferson
Republican* Party

Republican* Party

James Monroe
Republican* Party

Republican* Party
Whig Party

John Tyler
Whig Party

James K. Polk
Democratic Party

David Atchison**
Democratic Party

Zachary Taylor
Whig Party

Millard Fillmore
Whig Party

Franklin Pierce
Democratic Party

James Buchanan
Democratic Party

Abraham Lincoln
Republican Party

Jefferson Davis***
Democratic Party

Andrew Johnson
Republican Party

Ulysses S. Grant
Republican Party

Rutherford B. Hayes
Republican Party

James A. Garfield
Republican Party

Chester Arthur
Republican Party

Grover Cleveland
Democratic Party

Benjamin Harrison
Republican Party

Grover Cleveland
Democratic Party

William H. Taft
Republican Party

Woodrow Wilson
Democratic Party

Warren G. Harding
Republican Party

Calvin Coolidge
Republican Party

Herbert C. Hoover
Republican Party

Franklin D. Roosevelt
Democratic Party

Dwight D. Eisenhower
Republican Party

John F. Kennedy
Democratic Party

Lyndon B. Johnson
Democratic Party

Richard M. Nixon
Republican Party

Gerald R. Ford
Republican Party

James Earl Carter, Jr.
Democratic Party

Barack H. Obama
Democratic Party