Types of Chemical Reactions

ReviewA chemical equation describes a chemical

change.

The Law of Conservation of Mass says that the number and kind of atoms going INTO a chemical reaction must be the same as

the number and kind of atoms coming OUT.

Balancing an equation makes it obey the Law of Conservation of Mass.

The six types of chemical reactions we will discuss are:

SynthesisDecomposition

Single DisplacementDouble Displacement

Acid-BaseCombustion

Types of Reactions

Two or more substances combine to form one

substance.The general form is

A + X AX

Example:2Mg + O2 2MgO

Synthesis Reactions

Decomposition Reactions

One molecule breaks down to form two or more substances. The general form is

AX A + X

Example:2H2O 2H2 + O2

Single Displacement Reactions

A single element switches places with another element in a

chemical compound.

The general form is A + BX AX + B

Example:

Ni + 2AgNO3 2Ag + Ni(NO3)2

Example:

Ni + 2AgNO3 2Ag + Ni(NO3)2

Single Displacement Reactions

Ni + 2AgNO3 Nickel replaces the

metallic ion Ag+.

The silver becomes free silver and the nickel

becomes the nickel(II) ion.

Double Displacement Reactions

The cations of two compounds exchange

places with each other.

The general form is:AX + BY AY + BX

Double Displacement

Example:

NaOH + CuSO4

The Na+ and Cu2+ switch places.Na+ combines with SO4

2- to form Na2SO4.

Cu2+ combines with OH- to form Cu(OH)2

2NaOH + CuSO4 Na2SO4 + Cu(OH)2

Acid-BaseAcid-base reactions are double displacement reactions which takes place when an acid and

base react with each other.

HA + BOH → H2O + BA Acid Base

Example: HBr + NaOH → NaBr + H2OThe H+ ion in the acid reacts with the OH- ion in the

base, causing the formation of an ionic salt (NaBr) and water.

Combustion Reaction

When a compound containing carbon and hydrogen combines with oxygen, the products formed are heat, water,

and carbon dioxide.

CH4 + 2O2 CO2 + 2H2O

1) Does the reaction look like this: X + O2 CO2 + H2O ?

If yes - combustion reaction.

2) Is there only one product? If yes - synthesis reaction.

3) Is there only one reactant?If yes - decomposition reaction.

4) Are any reactants only one kind of element?

If yes - single displacement reaction.

5) Is water a product of this reaction? If yes - acid base reaction.

If not - double displacement reaction.

Learning Check...Classify each of the following

reactions:

H2 + Cl2 2HCl

Synthesis

Ca + 2H2O Ca(OH)2 + H2

Single displacement

Classify each of the following reactions:

2CO + O2 2CO2

Synthesis

2KClO3 2KCl + 3O2

Decomposition

Learning Check...

Classify each of the following reactions:

CH3SH + 3O2 CO2 + 2H2O + SO2

Combustion

Zn + 2HCl ZnCl2 + H2

Single displacement

Learning Check...