MOLE CONCEPT
The Mole as a Unit of Measurement
The Mole with Other Units of Measurements
Compare the mole with other units of measurements
When carrying out an experiment, a chemist cannot weigh out a single atom, ion, electron, proton or molecule of a substance. These particles are simply very small. A counting unit that is useful in practical chemistry must be used.
The standard unit is called one mole of the substance. One mole of each of these different substances contains the same number of the particles (atoms, molecules, ions, electrons, protons, neutrons, etc). That number per mole has been worked by several different experimental methods and is found to be 6.0 × 1023. The value 6.0 × 1023 is called Avogadro’s constant or Avogadro’s number and is abbreviated as L. It is named after the nineteenth-century Italian chemist, Amedeo Avogadro.
The value 6.0 × 1023 is obtained through the following relationship.The mass of one atom of carbon-12 is 1.993 × 10-23g. Then, the number of atoms present in 12g of carbon-12 is derived as follows:
1 atom = 1.993 × 10-23g
X atoms = 12g

\ X = 6.0 × 1023 atoms.
Therefore, the number of atoms in 12g of carbon-12 and hence the number of particles in a mole are 6.02 × 1023 atoms.
Hence, Avogadro’s number is the number of atoms in exactly 12g of carbon-12 isotope.One mole of any substance contains as many as many elementary particles as the Avogadro’s number (constant).
So, from the above explanation, the mole can be defined as the amount of a substance that contains as many elementary particles as the number of atoms present in 12g of carbon-12 isotope.
Substance Formula Relative formula mass, Mr Mass of one mole (molar mass) This mass (1 mole) contains
Carbon C 12 12g 6.0 × 1023 carbon atoms
Iron Fe 56 56g 6.0 × 1023 iron atoms
Hydrogen H2 2 × 1 = 2 2g 6.0 × 1023 molecules
Oxygen O2 2 × 16 = 32 32 6.0 × 1023 molecules
Water H2O (2×1) + 16 = 18 18g 6.0 × 1023 formula units
Magnesium oxide MgO 24 + 16 = 40 40g 6.0 × 1023 formula units
Calcium carbonate CaCO3 40+12+(3×16) = 100 100g 6.0 × 1023 formula units
Silicon oxide SiO2 28 + (2 × 16) = 60 60g 6.0 × 1023 formula units
Fe3+ Fe3+ 56 56g 6.0 × 1023 iron(III) ions
Cl- Cl- 35.5 35.5g 6.0 × 1023 chloride ions
e- e- - - 6.0 × 1023 electrons
The Mole as a Unit of Measurement
The Mole with Other Units of Measurements
Compare the mole with other units of measurements
When carrying out an experiment, a chemist cannot weigh out a single atom, ion, electron, proton or molecule of a substance. These particles are simply very small. A counting unit that is useful in practical chemistry must be used.
The standard unit is called one mole of the substance. One mole of each of these different substances contains the same number of the particles (atoms, molecules, ions, electrons, protons, neutrons, etc). That number per mole has been worked by several different experimental methods and is found to be 6.0 × 1023. The value 6.0 × 1023 is called Avogadro’s constant or Avogadro’s number and is abbreviated as L. It is named after the nineteenth-century Italian chemist, Amedeo Avogadro.
The value 6.0 × 1023 is obtained through the following relationship.The mass of one atom of carbon-12 is 1.993 × 10-23g. Then, the number of atoms present in 12g of carbon-12 is derived as follows:
1 atom = 1.993 × 10-23g
X atoms = 12g

\ X = 6.0 × 1023 atoms.
Therefore, the number of atoms in 12g of carbon-12 and hence the number of particles in a mole are 6.02 × 1023 atoms.
Hence, Avogadro’s number is the number of atoms in exactly 12g of carbon-12 isotope.One mole of any substance contains as many as many elementary particles as the Avogadro’s number (constant).
So, from the above explanation, the mole can be defined as the amount of a substance that contains as many elementary particles as the number of atoms present in 12g of carbon-12 isotope.
Substance Formula Relative formula mass, Mr Mass of one mole (molar mass) This mass (1 mole) contains
Carbon C 12 12g 6.0 × 1023 carbon atoms
Iron Fe 56 56g 6.0 × 1023 iron atoms
Hydrogen H2 2 × 1 = 2 2g 6.0 × 1023 molecules
Oxygen O2 2 × 16 = 32 32 6.0 × 1023 molecules
Water H2O (2×1) + 16 = 18 18g 6.0 × 1023 formula units
Magnesium oxide MgO 24 + 16 = 40 40g 6.0 × 1023 formula units
Calcium carbonate CaCO3 40+12+(3×16) = 100 100g 6.0 × 1023 formula units
Silicon oxide SiO2 28 + (2 × 16) = 60 60g 6.0 × 1023 formula units
Fe3+ Fe3+ 56 56g 6.0 × 1023 iron(III) ions
Cl- Cl- 35.5 35.5g 6.0 × 1023 chloride ions
e- e- - - 6.0 × 1023 electrons
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