Avogadro's number

Examples of Avogadro's number in the following topics:

• 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 defined as the number of elementary particles (molecules, atoms, compounds, etc.) per mole of a substance.
  • Avogadro's number is a similar concept to that of a dozen or a gross.
  • Avogadro's number is 6.022×1023 molecules.

• 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.
  • 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:
  • This can be written without a fraction in the denominator by multiplying the number of atoms by the reciprocal of Avogadro's number:

• 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.

• 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.
  • The law is named after Amedeo Avogadro who, in 1811, 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; 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.
  • 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.

• Equations of State

  • where C is a constant which is directly proportional to the amount of gas, n (representing the number of moles).
  • where k is Boltzmann's constant and N is the number of molecules.
  • (Since N = nNA, you can see that $R = N_Ak$, where NA is Avogadro's number. )
  • where P is the pressure, N is the number of molecules, m is the mass of the molecule, v is the speed of molecules, and V is the volume of the gas.

• The Effect of the Finite Volume

  • where NA is Avogadro's number and r is the radius of the molecule.

• Converting between Mass and Number of Moles

  • One mole (abbreviated mol) is equal to 6.022×1023 molecular entities (Avogadro's number), and each element has a different molar mass depending on the weight of 6.022×1023 of its atoms (1 mole).
  • By recognizing the relationship between the molar mass (g/mol), moles (mol), and particles, scientists can use dimensional analysis convert between mass, number of moles and number of atoms very easily.
  • To determine the number of atoms, convert the moles of Ni to atoms using Avogadro's number:
  • Given a sample's mass and number of moles in that sample, it is also possible to calculate the sample's molecular mass by dividing the mass by the number of moles to calculate g/mol.
  • Convert between the mass and the number of moles, and the number of atoms, in a given sample of compound

• Scientific Notation

  • Scientific notation is a more convenient way of writing very small or very large numbers.
  • To express a number in scientific notation, you move the decimal place to the right if the number is less than zero or to the left if the number is greater than zero.For example, in 456000, the decimal is after the last zero, so to express this in scientific notation, you would need to move the decimal to in between the 4 and 5.
  • The number of times you move the decimal place becomes the integer "b."
  • Therefore, our number in scientific notation would be: $4.56 \times 10^5$.
  • Learn to convert numbers into and out of scientific notation.

• Molar Mass of Compounds

  • Chemists can measure a quantity of matter using mass, but in chemical reactions it is often important to consider the number of atoms of each element present in each sample.
  • One mole (abbreviated mol) is equal to the number of atoms in 12 grams of carbon-12; this number is referred to as Avogadro's number and has been measured as approximately 6.022 x 1023.

• Early Models of the Atom

  • English chemist John Dalton (1766-1844) did much of this work, with significant contributions by the Italian physicist Amedeo Avogadro (1776-1856).
  • It was Avogadro who developed the idea of a fixed number of atoms and molecules in a mole.
  • This special number is called Avogadro's number in his honor ($6.022 \cdot 10^{23}$).