Types of Chemical

ReactionsSCH3U

GLOWS

Precipitate forms

Gives off a gas

Temperature changes

Light!

Success Criteria

OBy the end of this class you should:O Be able to classify a reaction as

synthesis, decomposition, single displacement, double displacement, combustion or neutralization.

O Be able to predict the products of synthesis and decomposition reactions.

Synthesis (Combination) Reaction

O Two or more reactants combine to form one product

A + B AB

Examples of synthesisO Metal  +  oxygen  →   metal oxide

O 2Mg(s)  +  O2(g)  →    2MgO(s)

O Nonmetal  +  oxygen  →    nonmetallic oxide O C(s)  +  O2(g)  →    CO2(g)

O Metal oxide  +  water  →    metallic hydroxide O MgO(s)  +   H2O(l)  →    Mg(OH)2(aq)

O Nonmetallic oxide  +  water  →    acid O CO2(g)  +  H2O(l)  →    H2CO3(aq) (one more oxygen)

O Metal + nonmetal  →    ionic compound (salt )O Mg(s)  +  Cl2(g)  →    MgCl2(s)

O A few nonmetals combine with each other.O 2P(s)  +  3Cl2(g)  →    2PCl3(g)

Oxides• When an element combines with

oxygen an oxide is formed• Metals react with oxygen to form

metal oxides• Metal oxides

•are always solids•react in water to form basic

solutions•are also called basic oxides

Metal Oxides - Example

Ca(s) + O2(g) CaO(s)

CaO(s) + H2O (l) Ca(OH)2(aq)

2 2metal oxide

basic solution

metal hydroxideYou did both these reactions in the Group I & II Elements Lab!

Oxides• Non-metals react with oxygen to

form non-metal oxides• Non-metal oxides

•are often gases or liquids•react in water to form acidic

solutions•are also called acidic oxides

Non-metal Oxides - Example

N2 (g) + O2(g) NO2 (g)

NO2 (g) + H2O (l) HNO3(aq) + NO (g)

2non-metal oxide

acidic solution

2

23

Summary of Predicting Synthesis Reactions

1. Metal oxides react with water to form metal hydroxides (bases)

2. Non-metal oxides react with water to form oxyacids (you just add 1 more oxygen to the oxide to form it’s oxyanion)

3. A metal and non-metal combine to form an ionic compound (a salt)

4. Some non-metals will combine to form covalent compounds.

Decomposition Reaction

O A single reactant is decomposed/broken down into two or more products.

AB A + B

Examples

O Metallic carbonates, when heated, form metallic oxides & CO2(g).

O MgCO3(s)  →    MgO(s)  +  CO

2(g)

O Most metallic hydroxides, when heated, decompose into metallic oxides and water. Ca(OH)

2(s)  →    CaO(s)  +  H

2O(g)

O Metallic chlorates, when heated, decompose into metallic chlorides and oxygen. 2KClO

3(s)  →    2KCl(s)  +  3O

2(g)

O Some acids, when heated, decompose into nonmetallic oxides and water.

O H2SO

4(aq)  →    H

2O(l)  +  SO

3(g)

O Some oxides, when heated, decompose.O 2HgO(s)  →    2Hg(l)  +  O

2(g)

O Some decomposition reactions are produced by electricity(electrolysis).

O 2H2O(l)  →    2H

2(g)  +  O

2(g)

O 2NaCl(l)  →    2Na(s)  +  Cl2(g)

How airbags work – sodium azide

Summary of Decomposition Reactions

1. All binary compounds break down into their elements

2. Metal carbonates decompose when heated to form metal oxides and carbon dioxide

3. Chlorates decompose when heated to form chloride compounds and oxygen gas

4. Bases (metal hydroxides) decompose when heated to a metal oxide and water

5. Oxyacids decompose when heated to a non-metal oxide and water