Types of Chemical Reactions 1. Synthesis Reactions Occur when two or more reactants (usually elements) join to form a compound. General Formula: A + B  AB (where A and B represent elements)

…can produce ionic or covalent compounds Magnesium metal reacts with oxygen gas to form solid magnesium oxide. 2Mg (s) + O2 (g)  2MgO (s) Covalent: Nitrogen gas and oxygen gas join to form gaseous dinitrogen monoxide. 2N2 (g) + O2 (g)  2N2O (g)

2. Decomposition are the opposite of synthesis reactions A compound breaks down into two or more products (often elements). General Formula: AB  A + B (where A and B represent elements)

Ionic and Covalent Compounds can decompose Table salt, sodium chloride, can be broken down into sodium metal & chlorine gas by melting salt at 800ºC and running electricity through it. 2NaCl(s)  2Na(s) + Cl2 (g) Covalent: By running electricity through water, the water molecules decompose into hydrogen & oxygen gases. 2H2O (l)  2H2 (g) + O2 (g)

3. Single Replacement When one element from a compound is replaced with a separate element Two types, based on whether the single element is a metal or a non-metal General Forms: A + BC  B + AC where A is a metal, or A + BC  C + BA where A is a non-metal

The Two Types: When A is a metal: Aluminum foil in a solution of copper II chloride produces solid copper and aqueous aluminum chloride. 2Al (s) + 3CuCl2 (aq)  3Cu (s) + 2AlCl3 (aq) When A is a non-metal: When fluorine gas is bubbled through a sodium iodide solution, iodine and aqueous sodium fluoride are produced. F2 (g) + 2NaI (aq)  I2 (g) + 2NaF (aq)

4. Double Replacement elements swap places between two compounds to form two new compounds. Two ionic solutions react to form a precipitate (solid) and another ionic solution General Form: AB + CD  AD + CB

Double Replacement Example: Solutions of potassium chromate and silver nitrate react to form a red precipitate, silver chromate, in a solution of potassium nitrate. K2CrO4(aq) + 2AgNO3(aq)  Ag2CrO4(s) + 2KNO3(aq) Note: the K and Ag switch places in the compounds.

5. Neutralization (a.k.a. Acid-Base reactions) occur when an acid and a base react to form a salt and water. acids (start with H) bases (end in OH, or begin with NH4) General Form: Acid + base  salt + water HX + MOH  MX + H2O (where X and M are elements)

Neutralization Examples: Sulphuric acid is used to neutralize aqueous calcium hydroxide: H2SO4 (aq) + Ca(OH)2 (aq)  CaSO4 (s) + 2HOH (l) Phosphoric acid helps to neutralize the compounds that cause rust, such as aqueous iron (II) hydroxide. 2H3PO4 (aq) + 3Fe(OH)2 (aq)  Fe3(PO4)2 (s) + 6H2O (l)

6. Combustion occurs when a compound or element reacts with oxygen Always makes CO2 and H2O (in grade 10 examples) Aka. hydrocarbon combustion General Form: CXHY + O2  CO2 + H2O

Combustion Examples: CH4 (g) + 2O2 (g)  CO2 (g) + 2H2O (g) Natural gas (methane) is burned in furnaces to heat homes CH4 (g) + 2O2 (g)  CO2 (g) + 2H2O (g) An acetylene torch is used to weld metals together 2C2H2 (g) + 5O2 (g)  4CO2 (g) + 2H2O (g) Carbohydrates like glucose combine with oxygen in our body to release energy C6H12O6 + 6O2  6CO2 + 6H2O