Chapter 5 key points
Chemistry 121, Spring 2015
Chemical reactions
• Chemical reactions (rxns) create new bonds and
break old ones
• Chemical rxns are written as chemical
equations, with the reaction arrow 
separating reactants (left) from products
(right); the mole (mol) is a fundamental unit of
a chemical in a reaction
• Stoichiometry allows the calculation of reaction
yields and limiting reactants; these require
balanced chemical equations
Chemical reaction classification
• Chemical rxns can be classified, and products
predicted
• Oxidation-reduction (redox) rxns in which new
bonds are made literally by moving electrons
• Metathesis rxns, also known as doublereplacement rxns, result in an insoluble
precipitate forming
• Decomposition rxns result when a compound
breaks down into smaller components
• A type of oxidation-reduction rxn is the
combustion rxn, in which oxygen gas is one of the
reactants