Quantitative chemistry

Balancing chemical equations Deriving empirical and molecular formulae The percentage of an element in a compound can be calculated from the relative mass of the element in the formula and the relative formula mass of the compound. The empirical formula of a compound can be calculated from the masses or percentages of the elements in a compound. Candidates should be able to calculate empirical formulae. Experiment to

Analysing substances

Elements and compounds can be detected and identified using instrumental methods. Instrumental methods are accurate, sensitive and rapid and are useful when the amount of a sample is very small. Paper Chromatography Chemical analysis can be used to identify additives in foods. Artificial colours can be detected and identified by paper chromatography. Knowledge of methods other than paper chromatography is not required, but questions may include

Atomic structure definitions

Mass number: The total number of protons and neutrons in an atom is called its mass number. Atomic number: the total number of protons (=electrons) in an atom. This number characterises the element type. Isotopes: Atoms of the same element can have different numbers of neutrons; these atoms are called isotopes of that element. Relative atomic mass (Ar): compares the mass of atoms of