Avogadro's Law

(noun)

under the same temperature and pressure conditions, equal volumes of all gases contain the same number of particles; also referred to as Avogadro's hypothesis or Avogadro's principle

Examples of Avogadro's Law in the following topics:

  • Avogadro's Law: Volume and Amount

    • Avogadro's Law states that at the same temperature and pressure, equal volumes of different gases contain an equal number of particles.
    • Avogadro's Law (sometimes referred to as Avogadro's hypothesis or Avogadro's principle) is a gas law; it states that under the same pressure and temperature conditions, equal volumes of all gases contain the same number of molecules.
    • In practice, real gases show small deviations from the ideal behavior and do not adhere to the law perfectly; the law is still a useful approximation for scientists, however.
    • By Avogadro's Law, this meant that hydrogen and oxygen were combining in a 2:1 ratio.
    • Using Avogadro's Law, this experiment confirmed that 2 hydrogen and 1 oxygen form 1 water molecule.

  • Avogadro's Number and the Mole

    • The mole is represented by Avogadro's number, which is 6.02×1023 mol-1.
    • Avogadro's number is a proportion that relates molar mass on an atomic scale to physical mass on a human scale.
    • Avogadro's number is a similar concept to that of a dozen or a gross.
    • Avogadro's number is 6.022×1023 molecules.
    • Avogadro's number is fundamental to understanding both the makeup of molecules and their interactions and combinations.

  • Avogador's Number

    • The number of molecules in a mole is called Avogadro's number (NA)—defined as 6.02x 1023 mol-1.
    • The actual number of atoms or molecules in one mole is called Avogadro's constant (NA), in recognition of Italian scientist Amedeo Avogadro .
    • Avogadro's number (N) refers to the number of molecules in one gram-molecule of oxygen.
    • The value of Avogadro's constant, NA , has been found to equal 6.02×1023 mol−1.
    • Avogadro's constant is a scaling factor between macroscopic and microscopic (atomic scale) observations of nature.

  • Equations of State

    • The ideal gas law is the equation of state of a hypothetical ideal gas (an illustration is offered in ).
    • It was first stated by Émile Clapeyron in 1834 as a combination of Boyle's law and Charles' law.
    • Boyle's law states that pressure P and volume V of a given mass of confined gas are inversely proportional:
    • (Since N = nNA, you can see that $R = N_Ak$, where NA is Avogadro's number. )
    • Therefore, we derive a microscopic version of the ideal gas law

  • Converting between Moles and Atoms

    • By understanding the relationship between moles and Avogadro's number, scientists can convert between number of moles and number of atoms.
    • The bridge between atoms and moles is Avogadro's number, 6.022×1023.
    • Avogadro's number is typically dimensionless, but when it defines the mole, it can be expressed as 6.022×1023 elementary entities/mol.
    • This form shows the role of Avogadro's number as a conversion factor between the number of entities and the number of moles.
    • Given a known number of moles (x), one can find the number of atoms (y) in this molar quantity by multiplying it by Avogadro's number:

  • The Effect of the Finite Volume

    • Real gases deviate from the ideal gas law due to the finite volume occupied by individual gas particles.
    • The ideal gas law is commonly used to model the behavior of gas-phase reactions.
    • The van der Waals equation modifies the ideal gas law to correct for this excluded volume, and is written as follows:
    • where NA is Avogadro's number and r is the radius of the molecule.

  • Constant Pressure

    • For an ideal gas, this means the volume of a gas is proportional to its temperature (historically, this is called Charles' law).
    • Using the ideal gas law PV=NkT (P=const),
    • The law says that the heat transferred to the system does work but also changes the internal energy of the system.
    • By noting that N=NAn and R = kNA (NA: Avogadro's number, R: universal gas constant), we derive:

  • Molar Mass of Gas

    • The molar mass of a particular gas is therefore equal to the mass of a single particle of that gas multiplied by Avogadro's number (6.02 x 1023 ).
    • The molar mass of an ideal gas can be determined using yet another derivation of the Ideal Gas Law: $PV=nRT$.
    • How to set up and solve ideal gas law problems that involve molar mass and converting between grams and moles.

  • Stastical Interpretation of Entropy

    • According the second law of thermodynamics, disorder is vastly more likely than order.
    • The various ways of formulating the second law of thermodynamics tell what happens rather than why it happens.
    • In a volume of 1 m3, roughly 1023 molecules (or the order of magnitude of Avogadro's number) are present in a gas.
    • (See (b). ) Indeed, it is so unlikely that we have a law saying that it is impossible, which has never been observed to be violated—the second law of thermodynamics.

  • Converting from One Unit to Another

    • Using physical laws, units of quantities can be expressed as combinations of units of other quantities.
    • This is based on physical laws that show that electric and magnetic fields are actually different manifestations of the same phenomenon.
    • Avogadro's number, 6.022 x 1023 atoms = 1 mole, will also help you in this problem.