Chemical Reactions Types of Reactions

Reactions and Energy Exothermic – energy releasing rxns Explosion, burning of fuel and rusting of iron Endothermic – energy absorbing rxns Cooking of food, electrolysis Changes of state – adding or releasing energy is common

Reactions and Energy Law of Conservation of Energy Energy can be converted from one form to another but the total quantity of energy is constant Remember Bond Energy to help this theory make sense

Types of Reactions Synthesis Decomposition Single Displacement Five main types of reactions Synthesis Decomposition Single Displacement Double Displacement Combustion One or more reactants combine to produce a new product X + Y  XY

Types of Reactions Decomposition A compound breaks down into two or more simpler compounds or elements. XY  X + Y

Types of Reactions Single Displacement One element takes the place (displaces) another element or compound. A + BX  AX + B or AX + Y  AY + X 2Na(s) + 2H2O(l)  2NaOH(aq) + H2(g) + thermal E

Types of Reactions A precipitate or water will be formed as products Double Displacement The cations of two different compounds exchange places, forming two new compounds WX + YZ  WZ + YX A precipitate or water will be formed as products

Reactions Involving Carbon Organic Chemistry Also all compounds containing carbon are organic (except CO2, CO and ionic carbonates) Hydrocarbon Used as fuels as reactions are exothermic Crude oil and natural gas When burned in a plentiful supply of oxygen it is known as complete combustion Hydrocarbon + oxygen  carbon dioxide + water Incomplete combustion = poor supply of oxygen Still exothermic, but not as much heat given off Carbon (soot) and carbon monoxide also given off