Structure 1.4 Counting particles by mass: The mole
Structure 1.4.1
Understandings:
  • The mole (mol) is the SI unit of amount of substance. One mole contains exactly the number of elementary entities given by the Avogadro constant.
Learning outcomes:
  • Convert the amount of substance, n, to the number of specified elementary entities.
Additional notes:
  • An elementary entity may be an atom, a molecule, an ion, an electron, any other particle or a specified group of particles.
  • The Avogadro constant NA is given in the data booklet. It has the units mol–1. ​
This video covers the mole concept. 
Structure 1.4.2
Understandings:
  • Masses of atoms are compared on a scale relative to 12C and are expressed as relative atomic mass Ar and relative formula mass Mr .
Learning outcomes:
  • Determine relative formula masses Mr from relative atomic masses Ar .
Additional notes:
  • Relative atomic mass and relative formula mass have no units.
  • The values of relative atomic masses given to two decimal places in the data booklet should be used in calculations.
This video covers relative atomic mass and relative molecular mass / relative formula mass. 
Please note that the IB now uses the term relative formula mass for both molecular and ionic compounds. 
Structure 1.4.3
Understandings:
  • Molar mass M has the units g mol–1
Learning outcomes:
  • Solve problems involving the relationships between the number of particles, the amount of substance in moles and the mass in grams.
Additional notes:
  • The relationship n =  m/M is given in the data booklet.
This video covers how to calculate the molar mass of a compound. 
This video covers how to calculate the amount (in mol) of a substance. Using the equation n = CV will be covered later in this section. 
This video covers how to convert between amount (in mol) and mass (in g). 
Structure 1.4.4
Understandings:
  • The empirical formula of a compound gives the simplest ratio of atoms of each element present in that compound.
  • The molecular formula gives the actual number of atoms of each element present in a molecule.
Learning outcomes:
  • Interconvert the percentage composition by mass and the empirical formula.
  • Determine the molecular formula of a compound from its empirical formula and molar mass.
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This video covers how to determine the percent composition by mass of an element in a compound. 
This video covers empirical and molecular formulas.
This video covers how to determine an empirical formula from percent composition by mass data. 
Structure 1.4.5
Understandings:
  • The molar concentration is determined by the amount of solute and the volume of solution.
Learning outcomes:
  • Solve problems involving the molar concentration, amount of solute and volume of solution.​
Additional notes:
  • The use of square brackets to represent molar concentration is required.
  • Units of concentration should include g dm–3 and mol dm–3 and conversion between these.
  • The relationship n = CV is given in the data booklet.
This video covers calculations involving concentrations of solutions. 
Structure 1.4.6
Understandings:
  • Avogadro’s law states that equal volumes of all gases measured under the same conditions of temperature and pressure contain equal numbers of molecules.
Learning outcomes:
  • Solve problems involving the mole ratio of reactants and/or products and the volume of gases.
This video covers Avogadro's law.