Types of Reactions

• There are so many different reactions that happen inside and outside the human body that chemists have tried to organize them into 5 major groups

Synthesis Reactions

• Two or more substances combine to form a more complex substance (synthesis)

• 2 or more reactants• Only one product

Synthesis reactions

• A + B AB

Synthesis Reactions

• A and B may be elements or compounds• AB is always a compound• N2 + 3H2 2NH3

• Produces ammonia to be used in many things, like fertilizer, nylon and plastic.

Examples

• 2Mg + O2 → 2MgO

• S + O2 → SO2

• 2Na + Cl2 → 2NaCl

Decomposition Reactions

• A complex substance breaks down into simple substances (opposite of synthesis)

• 2 or more products• Only 1 reactant.

Decomposition reactions

• AB A + B

Decomposition Reactions

• AB is always a compound• A & B may be elements or

compounds• 2HgO Hg + O2

• Bleaching hair, antiseptic, rocket fuel

Examples

• 2HgO → 2Hg + O2

• CaCO3 → CaO + CO2

Single Replacement Reactions• An uncombined element replaces

another element that is in a compound.• 1 of the reactants must be an

uncombined element and the other an ionic compound.

• 1 of the products must be an uncombined element and the other an ionic compound.

Single Replacement Reactions• A + BC AC + B

Single Replacement Reactions

• Zn + H2SO4 ZnSO4 + H2

Double Replacement Reactions• Two compounds exchange positive ions.• All reactants and products are ionic.• Will only occur if at least 1 compound is

removed from solution.• by precipitation• One product is water• One product is a gas that bubbles away

Double Replacement Reactions• AB + CD AD + CB

Double Replacement Reactions

• 2NaOH + H2SO4 Na2SO4 + 2HOH

Combustion Reactions

• A substance burns in the presence of oxygen to produce carbon dioxide and water.

• C3H8 + 5 O2 3 CO2 + 4H2O• Propane burns (with the help of

oxygen) to produce carbon dioxide and water

Combustion Reaction

• Be careful not to confuse combustion reactions with single replacement reactions.

Let’s practice!!!!!

• 3Mg + 2FeCl3 2Fe + 3MgCl2• 2Fe + 3F2 2FeF3

• SO3 + H2O H2SO4

• 2HI H2 + I2• Li2CrO4 + BaCl2 2LiCl + BaCrO4

• CH4 + 2O2 CO2 + 2H2O• 2Al2O3 4Al + 3O2