Types of Chemical Reactions

Synthesis Type 1: SYNTHESIS Definition: Two or more reactants combine to form one product Key sign: One product General Structure: A + X  AX Examples: CO + O2  CO3 2Mg + O2  2MgO

Decomposition Type 2: DECOMPOSITION Definition: One reactant breaks down into two or more products Key sign: One reactant General Structure: AX  A + X Examples: H2CO3  CO2 + H2O NCl3  N2 + Cl2

Single Replacement (Displacement) Type 3: SINGLE REPLACEMENT (OR DISPLACEMENT) Definition: A single element replaces another element in a compound Key sign: One single element and a compound on both sides of the equation General Structure: A + BX  AX + B Examples: H2SO4 + Ca  CaSO4 + H2 Li + H2O  LiOH + H2

Double Replacement (Displacement) Type 4: DOUBLE REPLACEMENT (OR DISPLACEMENT) Definition: Two ions replace each other to form two different compounds Key sign: Two compounds on both sides of the equation General Structure: AX + BY  AY + BX Examples: CaCl2 + K3PO4  Ca3(PO4)2 + KCl Al2(SO4)3 + Ca(OH)2  Al(OH)3 + CaSO4 Special type of double replacement reaction is an acid-base reaction. An acid reacts with a base and the products are always a salt and water (H2O).

Combustion Type 5: COMBUSTION Definition: A chemical burns in oxygen to produce light/heat Key sign: Oxygen is a reactant, carbon dioxide and water are products (or vice versa) General Structure: A + O2  CO2 + H2O Examples: C10H22 + O2  CO2 + H2O CH4 + O2  CO2 + H2O

Questions to Ask… Does the reaction have oxygen as one of the reactants and carbon dioxide and water as products? If yes, then combustion. Does your reaction have two or more chemicals combining to form one chemical? If yes, then synthesis. Does your reaction have one molecule falling apart to create several small ones? If yes, then decomposition. Does your reaction have any molecules that are only one element? If yes, then single displacement. Does your reaction have two molecules that switch partners? If yes, then double displacement.