IB Chemistry HL 100113

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.

Convert the amount of substance, $n$, to the number of specified elementary entities.

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 ($N_A$) is given in the data booklet. It has the units mol ^-1.

Masses of atoms are compared on a scale relative to 12C and are expressed as relative atomic mass ($A_{\text{r}}$) and relative formula mass ($M_{\text{r}}$).

Determine relative formula masses ($M_{\text{r}}$) from relative atomic masses ($A_{\text{r}}$)

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.

Molar mass M has the units g mol$^{-1}$.

Solve problems involving the relationships between the number of particles, the amount of substance in moles and the mass in grams.

The relationship $n = \dfrac{m}{M}$ is given in the data booklet.

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.

Interconvert the percentage composition by mass and the empirical formula.

Determine the molecular formula of a compound from its empirical formula and molar mass.

The molar concentration is determined by the amount of solute and the volume of solution.

Solve problems involving the molar concentration, amount of solute and volume of solution.

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.

Avogadro’s law states that equal volumes of all gases measured under the same conditions of temperature and pressure contain equal numbers of molecules.

Solve problems involving the mole ratio of reactants and/or products and the volume of gases.