Classifying Chemical Reactions

Classifying Chemical Reactions Reactions are either classified by: how much energy is given off or absorbed how the atoms are rearranged Chemical Reactions and Energy Exothermic Reactions produce energy (heat, light, sound) e.g. CH4(g) + O2(g)  H2O(g) + CO2(g) + energy Endothermic Reactions absorb energy (heat, light, sound) e.g. CaCO3(s) + energy  CaO(s) + CO2(g)

Chemical Reactions and Atom Rearrangement Synthesis Reactions (Combination) 2 or more substances combine to form a compound General Formula: A + B  AB 1 PRODUCT e.g. S(s) + O2(g)  SO2(g) 2 elements 2SO2(g) + O2(g)  2SO3(g) 1 element, 1 compound SO3(g) + H2O(l)  H2SO4(g) 2 compounds Decomposition Reactions 1 substance breaks down into 2 or more simpler substances General Formula: AB  A + B 1 REACTANT e.g. 2H2O(l)  2H2(g) + O2(g)

Single Replacement Reactions (Displacement) A combined element in a compound is replaced by an uncombined element. General Formula: Z + AB  AZ + B Metals replace metals; Non-metals replace Non-metals e.g. Br2(l) + 2NaCl(aq)  2NaBr(aq) + Cl2(g) 2Al(s) + Fe2O3(s)  2Fe(l) + Al2O3(s) Double Replacement Reactions (Ionic) Elements in different compounds replace each other (exchange places) General Formula: AB + XY  AY + XB e.g. 2KI(aq) + Pb(NO3)2(aq)  PbI2(s) + 2KNO3(aq) 2KI(aq) + Pb(NO3)2(aq)  PbI2(s) + 2KNO3(aq) One of the products often forms a precipitate. (an insoluble solid that separates from the solution)

Neutralization (Acid-Base) A type of double replacement reaction that involves an acid reacting with a base to produce water and a salt. General Formula: Acid + Base  Water + Salt e.g. HCl(aq) + NaOH(aq)  HOH(l) + NaCl(aq) HCl(aq) + NaOH(aq)  HOH(l) + NaCl(aq) Combustion A special type of exothermic reaction where oxygen is a reactant and oxides are produced with a large amount of energy. e.g. CH4(g) + 2O2(g)  CO2(g) + 2H2O(l) + energy 2H2(g) + O2(g)  2H2O(l) + energy 2Mg(s) + O2(g)  2MgO(s) + energy

Assignment In Class: Homework: Classify Workbook Pages 105 & 106 Balance Workbook Pages 105 & 106 Classify Workbook Pages 107 & 108