Chemical Reactions SCH 3U Unit 2 Part 3

Classifying Reactions Most chemical reactions can be grouped or organized into 5 categories. Synthesis Decomposition Single Displacement Double Displacement Combustion

Synthesis Reactions A synthesis reaction occurs when two or more small substances combine to produce a larger substance. A + B  AB Only 1 product!

Types of Synthesis Two elements may combine to form a compound: hydrogen + oxygen  water 2H 2 + O 2  2H 2 O Remember to criss-cross new subscripts!

Two compounds may combine to form a larger compound: carbon dioxide + water  carbonic acid CO 2 + H 2 O  H 2 CO 3 Types of Synthesis

General Synthesis Reactions Nonmetal oxide + water  oxyacid Metal oxide + water  metal hydroxide Na 2 O + H 2 O  2NaOH SO 2 + H 2 O  H 2 SO 3

Synthesis of Acids and Bases Na 2 O + H 2 O  NaOH MgO + H 2 O  Mg(OH) 2 SO 2 + H 2 O  H 2 SO 3 Cl 2 O 5 + H 2 O  HClO 3

Applications of Synthesis Rusting Iron combines with oxygen in the air to form iron (III) oxide or rust. The rust then flakes away, exposing new metal underneath to the oxygen.

Acid Rain Non-metal oxides found in the air due to pollution combine with water to form acids. These acids fall to the ground as acid rain. Applications of Synthesis

Polymerization Small molecules are linked together to form long-chain molecules called polymers. Applications of Synthesis

Decomposition Reactions A decomposition reaction occurs when one larger substance breaks up into two or more smaller substances. AB  A + B Only 1 reactant! Decomposition reactions are the opposite to synthesis!!

Types of Decomposition A compound may decompose to produce two elements water  hydrogen + oxygen 2H 2 O  2H 2 + O 2 Remember to make the seven sisters diatomic!

A large compound may decompose to produce two smaller compounds Types of Decomposition potassium  potassium + oxygen chlorate oxide KClO 3  KCl + O 2

General Decomposition Reactions Metal carbonates decompose to produce a metal oxide and carbon dioxide CaCO 3  CaO + CO 2 calcium  calcium + carbon carbonate oxide dioxide

Applications of Decomposition Production of Hydrogen The decomposition of water is used in the production of hydrogen for hydrogen fuel cells.

Return of atmospheric carbon Decomposition reactions release carbon dioxide back into the atmosphere to re-enter the carbon cycle. Applications of Decomposition

Pg 125 # 7-10 Pg 127 # Pg 132 #13, 15, 16 Pg 134 # Pg 136 # 2, 4, 7, 8, 15 Time to get to Work