Note:

IGCSE Chemistry Notes on Stoichiometry

Syllabus Objectives:

4.1 Stoichiometry

Core 

• Use the symbols of the elements and write the formulae of simple compounds 
• Deduce the formula of a simple compound from the relative numbers of atoms present 
• Deduce the formula of a simple compound from a model or a diagrammatic representation 
• Construct word equations and simple balanced chemical equations
• Define relative atomic mass, Ar , as the average mass of naturally occurring atoms of an element on a scale where the 12C atom has a mass of exactly 12 units
• Define relative molecular mass, Mr , as the sum of the relative atomic masses. (Relative formula mass or Mr will be used for ionic compounds.) (Calculations involving reacting masses in simple proportions may be set. Calculations will not involve the mole concept.)

Supplement 

• Determine the formula of an ionic compound from the charges on the ions present 
• Construct equations with state symbols, including ionic equations
• Deduce the balanced equation for a chemical reaction, given relevant information

4.2 The mole concept

Supplement 

• Define the mole and the Avogadro constant 
• Use the molar gas volume, taken as 24dm3 at room temperature and pressure 
• Calculate stoichiometric reacting masses, volumes of gases and solutions, and concentrations of solutions expressed in g /dm3 and mol/dm3 . (Calculations involving the idea of limiting reactants may be set.
• Questions on the gas laws and the conversion of gaseous volumes to different temperatures and pressures will not be set.) 
• Calculate empirical formulae and molecular formulae • Calculate percentage yield and percentage purity