GCSE Chemistry (AQA)

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Moles

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Quantitative chemistry Use of amount of substance in relation to masses of pure substances

Moles

5:39 Moles, Mass, and Balanced Equations
Spec 4.3.2.1
Previous Uncertainty Next Using Moles to Balance Equations
  • Masses of individual atoms and molecules are too small for practical calculations.
  • A single carbon atom's mass is 1.99 x 10^-23 grams, requiring 26 decimal places.
  • Chemistry uses moles to measure chemical amounts for easier calculations.
  • Moles can quantify atoms, molecules, ions, and electrons, used in formulae and equations.
  • The mass of one mole of a substance in grams equals its relative formula mass.
  • Example: Carbon dioxide (CO2) has a relative formula mass of 44, so one mole weighs 44 grams.
  • The symbol for the unit mole is MOL.
  • One mole of a substance contains the same number of particles as one mole of any other substance.
  • Example: One mole of carbon (12 grams) and one mole of CO2 (44 grams) contain the same number of particles.
  • The number of particles in a mole is known as the Avogadro constant, 6.02 x 10^23.
  • Avogadro constant applies to atoms, molecules, or ions, regardless of the substance.
  • Understanding moles and the Avogadro constant is crucial for exams.

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