Types of Chemical Reactions (there are a lot, millions of different reactions). Scientists classify reactions into several general categories to allow predictions to be made. 5 Major Types of Reactions Iron + Sulfur Reaction Elephant Toothpaste

1. Synthesis Reaction Direct combination two or more simpler substances combine chemically to form a more complex substance. general formula: A + B  AB

1. Synthesis Reaction - Examples Na + Cl  NaCl (sodium) + (chlorine)  (sodium chloride) [table salt] Synthesis Reaction

2. Decomposition a more complex substance breaks down chemically to a simpler substance. general formula: AB  A + B

2. Decomposition - Examples 2H20  2H2 + O2 (water)  (hydrogen gas) + (oxygen gas) Decomposition Reaction

3. Single Replacement Displacement an element will replace another element in a compound, almost always occurs in a solution. general formula: A + BX  B + AX

3. Single Replacement - Examples Fe + CuSO4  Cu + FeSO4 (iron) + (copper sulfate)  (copper) + (iron (II) sulfate) Single Replacement Reaction

4. Double Replacement Displacement the anions and cations in two compounds (in solution) change partners. General formula: AX + BY  AY + BX

4. Double Replacement - Examples AgNO3(aq) + NaCl(aq)  AgCl + NaNO3 (silver nitrate) + (sodium chloride)  (silver chloride) + (sodium nitrate) NaCl + KF  NaF + KCl (sodium chloride) + (potassium fluoride)  (sodium fluoride) + (potassium chloride) Double Replacement Reaction

5. Combustion Burning Combustion: rapid reaction of a substance with oxygen. General Formula: CxHy + O2  CO2 + H2O

5. Combustion - Examples C3H8 + 5O2  3CO2 + 4H2O Combustion Reaction (propane) + (oxygen gas)  (carbon dioxide) + (water) Combustion Reaction