Stoichiometry

C3.1 Formulae 1 State the formulas of the elements and compounds named in the subject content 2 Define the molecular formula of a compound as the number and type of atoms in one molecule 3 Deduce the formula of a simple molecular compound from the relative numbers of atoms present in a model or a diagrammatic representation 6 Deduce the formula of an ionic compound from the relative numbers of the ions present in a model or a diagrammatic representation or from the charges on the ions 4 Construct word equations to show how reactants form products 5 Balance and interpret simple symbol equations, including state symbols 7 Construct symbol equations with state symbols, including ionic equations 8 Deduce the symbol equation with state symbols for a chemical reaction, given relevant information C3.2 Relative masses of atoms and molecules 1 Describe relative atomic mass, Ar, as the average mass of the isotopes of an element compared to 1/12th of the mass of an atom of 12C 2 Define relative molecular mass, Mr, as the sum of the relative atomic masses. Relative formula mass, Mr, will be used for ionic compounds 3 Calculate reacting masses in simple proportions C3.3 The mole and the Avogadro constant State that concentration can be measured in g/dm3 State that the mole, mol, is the unit of amount of substance and that one mole contains 6.02 × 1023 particles, e.g. atoms, ions, molecules; this number is the Avogadro constant Use the relationship amount of substance (mol) / mass (g) = molar mass (g/mol) to calculate: amount of substance mass molar mass relative atomic mass or relative molecular / formula mass Use the molar gas volume, taken as 24 dm3 at room temperature and pressure, r.t.p., in calculations involving gases Calculate stoichiometric reacting masses, limiting reactants, volumes of gases at r.t.p., including conversion between cm3 and dm3