Types of Chemical Reactions

Movie: types of chemical reactions: http://www.youtube.com/watch?v=i-HHvx1VC_8

http://www.youtube.com/watch?v=ritaljhhk7s

Learning OutcomesIdentify, give evidence for, predict products of, and classify the following types of chemical reactions:

1. Synthesis (Combination)

2. Decomposition

3. Single Replacement

4. Double Replacement

5. Neutralization (acid/base)

6. Combustion

Vocabulary Synthesis

Decomposition

Neutralization

Single displacement

Double displacement

Combustion

A chemical change: any change in which a new substance is formed.

Evidence of a Chemical Change:

Release of energy as heat (exothermic)

Release of energy as light

Change in colour

Formation of a gas

Change in odour…

Chemical Reactions

1. Synthesis: A + B AB

2. Decomposition: AB A + B

3. Neutralization: Acid(H) + Base(OH) Salt + H(OH)

4. Single displacement: A + BC AC + B

5. Double displacement: AB + CD AD + CB

6. Combustion: AB + oxygen CO2 + H2O

Types of Chemical Reactions

A + B AB where A and B represent elements

– The elements may form ionic compounds, like…

– Sodium metal and chlorine gas combine to form sodium chloride.

2Na + Cl2 2NaCl

(c) McGraw Hill Ryerson 2007

See pages 258 - 259

Sodium added to chlorine gas

Synthesis Reactions

Synthesis reactions are also known as COMBINATION reactions.Two or more reactants (usually elements) join to form a compound.

Synthesis Reaction

Example C + O2 CO2

OO C + O O C

General: A + B AB

OTHER EXAMPLES…

1. Elements that form ionic compounds: Magnesium metal reacts with oxygen gas to form magnesium oxide.

2Mg + O2 2MgO

2. Elements that form covalent compounds: Nitrogen gas and oxygen gas combine to

form dinitrogen monoxide.

2N2 + O2 2N2O

(c) McGraw Hill Ryerson 2007

Synthesis Reactions

SYNTHESIS REACTION (iron + sulphur):http://www.youtube.com/watch?v=A5H6DVe5FAI

• Decomposition reactions are the opposite of synthesis reactions.– A compounds breaks down into two or more

products (often elements).

AB A + B where A and B represent elements

1. Ionic compounds may decompose to produce elements, like the following:

• Table salt, sodium chloride, can be broken down into sodium metal and chlorine gas by melting salt at 800ºC and running electricity through it.

• 2NaCl 2Na + Cl2(c) McGraw Hill Ryerson 2007

See page 260

Decomposition Reactions

Types: Decomposition

Example: NaCl

General: AB A + B

Cl Na Cl + Na

Types: Decomposition

Example 2HgO

O Hg

O Hg

Hg

O O Hg

+

General: AB A + B

2. Covalent compounds may decompose into elements, like the following:

• By running electricity through water, the water molecules decompose into hydrogen and oxygen gases.

• 2H2O 2H2 + O2

(c) McGraw Hill Ryerson 2007

Decomposition Reactions

DECOMPOSITION REACTION:

http://www.youtube.com/watch?v=hWiWjWHdHXM

• Single replacement reactions replace one element from a compound with another element.– A compound and an element react, and the

element switches places with part of the original compound.

A + BC B + AC where A is a metal, or

A + BC C + BA where A is a non-metal

(c) McGraw Hill Ryerson 2007

See page 261

Single Replacement Reactions

Types: Single replacement

Example: Zn + CuCl2

ZnClCl Cu +

General: AB + C AC + B

ClCl Zn Cu+

1. When A is a metal:• Aluminum foil in a solution of copper(II)

chloride produces solid copper and aluminum chloride.

• 2Al + 3CuCl2 3Cu + 2AlCl3

2. When A is a non-metal:• When fluorine is bubbled through a sodium

iodide solution, iodine and sodium fluoride are produced.

• Fl2 + 2NaI I2 + 2NaF

Single Replacement Reactions

SINGLE REPLACEMENT:http://www.youtube.com/watch?v=hKtynbVtMKc

• Double replacement reactions swap elements between 2 compounds that react together to form two new compounds.– Two compounds react, with elements switching

places between the original compounds.

AB + CD AD + CB

(c) McGraw Hill Ryerson 2007

See page 262

Double Replacement Reactions

Types: Double replacement

Example: MgO + CaS

AB + CD AD + CB

SOMg Ca

+O S

Mg Ca+

– When potassium chromate and silver nitrate react, they form a red precipitate, silver chromate, in a solution of potassium nitrate.

– K2CrO4 + 2AgNO3 Ag2CrO4 + 2KNO3

(c) McGraw Hill Ryerson 2007

silver chromate

Double Replacement Reactions

Two solutions react to form a precipitate (solid) and another solution.

Ionic solution + ionic solution ionic solution + ionic solid.

AB + CD AD + CB

DOUBLE REPLACEMENT:http://www.youtube.com/watch?v=opY3FLrPTa4

• Neutralization reactions occur when an acid (most compounds starting with H) and a base (most compounds ending in OH) react to form a salt and water.

• Neutralization reactions are a type of double replacement.

• Acid + base salt + water

HX + MOH MX + H2O where X and M are elements

(c) McGraw Hill Ryerson 2007

See page 263

Neutralization Reactions

1. Sulfuric acid is used to neutralize calcium hydroxide:• H2SO4 + Ca(OH) 2 CaSO4 + 2H2O

2. Phosphoric acid helps to neutralize the compounds that cause rust, such as iron(II) hydroxide.• H3PO4 + 3Fe(OH)2 Fe3(PO4)2 + 6H2O

(c) McGraw Hill Ryerson 2007

See page 263

Neutralization Reactions

NEUTRALIZATION:

http://www.youtube.com/watch?v=_P5hGzA6Vb0

• Combustion reactions occur when a compound or element react with oxygen to release energy and produce an oxide.– Also sometimes referred to as hydrocarbon

combustion.

CXHY + O2 CO2 + H2O where X and Y represent integers

(c) McGraw Hill Ryerson 2007

See page 264

Combustion Reactions

METHANOL + oxygen: http://www.youtube.com/watch?v=98JuJ-G1qXY&feature=related

1. Natural gas (methane) is burned in furnaces to heat homes.

CH4 + O2 CO2 + 2H2O + energy

2. An acetylene torch is used to weld metals together.

2C2H2 + 5O2 4CO2 + 2H2O + energy

3. Carbohydrates like glucose combine with oxygen in our body to release energy.

C6H12O6 + 6O2 6CO2 + 6H2O + energy

(c) McGraw Hill Ryerson 2007

Acetylene torch

Combustion Reactions

(c) McGraw Hill Ryerson 2007

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SUMMARY OF REACTIONSMovie of five of the main reactions http://www.youtube.com/watch?v=tE4668aarck