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