Gas constants and their relationships

Gas Constants & their values

  • The Avogadro constant (NA) = 6.02 × 1023 particles per mole
  • The molar gas constant or universal gas constant (R) = 8.31 J mol−1 K−1
  • The Boltzmann constant (kb) = 1.38 × 10−23 J K−1

Gas constants and their relationships

  • For an ideal gas of n moles and N molecules:
    number of molecules (N) = number of moles (n) x Avogadro constant (NA)
    => N = n NA
  • number of moles (n) =number of molecules (N) /Avogadro constant (NA)
    n=N/NA
  • Boltzmann constant(kb) = molar gas constant(R) / Avogadro constant (NA)
    kb = R / NA
  • R = NA kb
    molar gas constant or Universal Gas Constant(R) = Avogadro constant (NA) x Boltzmann constant (kb)

Some examples & facts

  • In 1 mole of hydrogen (2 g) there are 6.02 × 1023 molecules (hydrogen exists as H2).
  • In 1 mole of oxygen (32 g) there are 6.02 × 1023 molecules (oxygen exists as O2).
  • In 1 mole of copper (63 g) there are 6.02 × 1023 atoms.
  • In 1 mole of uranium-235 (235 g) there are 6.02 × 1023 atoms.
  • For example, if we have 2 kg of uranium in a fuel rod we have 2000 / 235 = 8.51 moles, and this contains 8.51 × 6.02 × 1023 = 5.12 × 1024 atoms and so 5.12 × 1024 uranium nuclei.

Gas constants and their relationships
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