Synthesis Reaction

• Two or more substances combine to form a more complex substance

2 Mg (s) + O2 (g) 2 MgO (s)

Decomposition Reaction:

• A complex substance breaks down into its parts

• One reactant yields (forms) 2 or more products

• SYNTHESIS and DECOMPOSITION reactions are OPPOSITES

+

turtle egg turtleegg shell

CaCO3 (s) CaO (s) + CO2 (g)

Single Replacement Reaction:

• A single uncombined element replaces another in a compound

• Two reactants yield two products

Zn (s) + 2 HCl (aq) ZnCl2 (aq) + H2 (g)

Double Replacement Reaction:

• Parts of two compounds switch places to form two new compounds

• Two reactants yield two products.

They’ve swapped their ‘cats’!

Al2(SO4)3 + 6 NH4OH 3 (NH4)2SO4 + 2Al(OH)3

Reactants: oxygen gas and a hydrocarbon

Products: CO2 and H2O

___ C6H6 + ___ O2 ___ CO2 + ___ H2O6 32 15 12 6

• Balance carbons

• Balance hydrogens

• Check oxygen count

12 + 3 = 15 oxygens

Odd number of oxygens, so multiply through by 2

24 + 6 = 30 oxygens

Zn (s) + 2 HCl (aq) ZnCl2 (aq) + H2 (g)

Cu (s) + 2 AgNO3 Cu(NO3)2 + 2 Ag (s)

Note that the reactions won’t work the other way around!!!

The reaction only takes place if the element on the reactant side is ‘hotter’ than the element that ends up being formed.

The higher up on the activity series the element is, the ‘hotter’ it is.

Single Replacement Reaction:

• A single uncombined element replaces another in a compound

• Two reactants yield two products

Zn (s) + 2 HCl (aq) ZnCl2 (aq) + H2 (g)

Metals

LithiumPotassium

CalciumSodium

MagnesiumAluminum

ZincChromium

IronNickel

TinLead

Hydrogen*CopperMercury

SilverPlatinum

Gold

Halogens

FluorineChlorineBromine

Iodine

Decreasing Activity

Double Replacement Reaction:

• Parts of two compounds switch places to form two new compounds

• Two reactants yield two products.

They’ve swapped their ‘cats’!

Al2(SO4)3 + 6 NH4OH 3 (NH4)2SO4 + 2Al(OH)3

Reactants: oxygen gas and a hydrocarbon

Products: CO2 and H2O

___ C6H6 + ___ O2 ___ CO2 + ___ H2O6 32 15 12 6

• Balance carbons

• Balance hydrogens

• Check oxygen count

12 + 3 = 15 oxygens

Odd number of oxygens, so multiply through by 2

24 + 6 = 30 oxygens

+

Synthesis/Combination

Decomposition

Single-Replacement Activity Series

A + B AB

AB A + B

A + BC AC + B

Double-Replacement Solubility Rules

CombustionO2

+ +

hydrocarbon CO2 H2OO2

AB + CD CB + AD

A redox reaction is one in which the reactants’ oxidation numbers change.

What are the oxidation numbers of the metals in the reaction below?

2 FeCl3 + SnCl2 2 FeCl2 + SnCl4

+3 +2 +2 +4

The iron’s charge has become more negative, so it is reduced.

The tin’s charge has become more positive, so it is oxidized.

reduced

oxidized

0

+2

+4

+6

+8

-2

-6

-4

0

+2

+4

+6

+8

-2

-6

-4

Fe Sn

x + 3(-1) = 0x + 2(-1) = 0

x + 2(-1) = 0x + 4(-1) = 0

Which reactant is oxidized and which is reduced in the following?

2) Cu + 2AgNO3 Cu(NO3)2 + 2Ag0 +1 +2 0

reduced

oxidized

1) Cl2 + SnCl2 SnCl4

0 -1-1

reduced

oxidized

+2 +4

3) 2KClO3 2KCl + 3O2

-2 -1 0+5

reduced

oxidized

SynthesisSynthesis

Single-replacementSingle-replacement

DecompositionDecomposition

Note that a redox reaction can also be another type of reaction.

+1 + x + 3(-2) = 0