1. Chemical Reactions
There are thousands of different chemical reactions that can take place in nature and in industrial processes
It would be difficult to memorize all of them!
By classifying reactions, we can predict the products that will form

2. Types of Reactions
These are the types of chemical reactions we will talk about:
Synthesis reactions
Decomposition reactions
Single displacement (replacement) reactions
Double displacement(replacement) reactions
Combustion
You need to be able to identify the type of reaction and predict the product(s)

3. Steps to Writing Reactions Step 1
Identify the type of reaction from clues that are available. Write a word equation.
Example: The combustion of methane gas in air forms water and carbon dioxide.
Word equation:
Methane + oxygen  water + carbon dioxide

4. Step 2
Write a generic equation following the rules from Reaction Types.
Write the reactants and products using appropriate symbols and formulas.
Balance charges for ionic compounds using the Common Ion Chart or Periodic Table.
Don’t forget diatomic elements! (BrINClHOF).
Example:
Methane + oxygen  water + carbon dioxide
CH4 + O2  H2O + CO2

5. Step 3 Balance the equation by adjusting the coefficients.
Example: CH4 + O2  H2O + CO2
Balanced: CH4 + 2O2  2H2O + CO2

6. Step 4
Confirm that the equation is balanced by checking the number of atoms of each element on both sides of the equation.
Example: CH4 + 2O2  2H2O + CO2
Reactants Products
1C 1C
4H 4H
4O 2O + 2O = 4O
This equation is balanced!

7. 1. Synthesis reactions
Synthesis reactions occur when two substances (sometimes elements) combine and form a compound. (Sometimes these are called combination or addition reactions.)
reactant + reactant  1 product
Basically: A + B  AB
Example: 2H2 + O2  2H2O
Example: C + O2  CO2

8. Synthesis Reactions
Here is another example of a synthesis reaction

9. Practice
Predict the products. Write and balance the following synthesis reaction equations.
Sodium metal reacts with chlorine gas
Na(s) + Cl2(g) 
Solid Magnesium reacts with fluorine gas
Mg(s) + F2(g) 
Aluminum metal reacts with fluorine gas
Al(s) + F2(g) 

10. 2. Decomposition Reactions
Decomposition reactions occur when a compound breaks up into the elements or in a few to simpler compounds
1 Reactant  Product A+ Product B
In general: AB  A + B
Example: 2 H2O  2H2 + O2
Example: 2 HgO  2Hg + O2

11. Decomposition Reactions when heated
Metallic Carbonates give off metallic oxide and Carbon Dioxide: Li2CO3  Li2O + CO2
Metallic Hydroxides give off metallic oxide and water: Ba(OH)2  BaO + H2O
Metallic Chlorates give off metallic chloride and O2: NaClO3  2 NaCl + 3 O2
Mineral Acids make water and nonmetal oxide: H2CO3  H2O + CO2
Metal Oxides release O2: 2PbO2  2PbO + O2
Electrolysis breaks compounds into elements: KCl  2K + Cl2

12. 2. Decomposition Reactions
Another view of a decomposition reaction:

13. 3. Single Replacement Reactions A + BX  B + AX
Active Metals replacing metals forming a
salt. (Check the Activity Series) Na > Ag
Na˚ + AgNO3  Ag˚ + NaNO3

14. More Single Replacement Reactions
Very Active Metals react w/ water releasing H2 and metallic hydroxide
(check Activity Series): K + 2H2O  H KOH
Metals and Acids form H2 and salts:
Zn HCl  H2 + ZnCl2
Halogen-Halide Replacement (check Activity Series):
F RbBr  Br RbF

15. Single Replacement Reactions
Aluminum metal reacts with Copper II Nitrate
Al Cu(NO3)2 

16. 4. Double Replacement Reactions
Double Replacement Reactions occur when a metal replaces a metal in a compound and a nonmetal replaces a nonmetal in a compound
Compound + compound  product + product
AB + CD  AD + CB

17. Double Replacement Reactions
Think about it like “foil”ing in algebra, first and last ions go together + inside ions go together
Example:
AgNO3(aq) + NaCl(s)  AgCl(s) + NaNO3(aq)
Another example:
K2SO4(aq) + Ba(NO3)2(aq)  KNO3(aq) + BaSO4(s) 2

18. Practice
Predict the products. Be sure to check the charges. Balance the equation
HCl(aq) + AgNO3(aq) 
CaCl2(aq) + Na3PO4(aq) 
Pb(NO3)2(aq) + BaCl2(aq) 
FeCl3(aq) + NaOH(aq) 
H2SO4(aq) + NaOH(aq) 
KOH(aq) + CuSO4(aq) 

19. 5. Combustion Reactions
Combustion reactions occur when a hydrocarbon reacts with oxygen gas.
This is also called burning!!! In order to burn something you need the 3 things in the “fire triangle”: 1) Fuel (typically hydrocarbon) 2) Oxygen (supports combustion) 3) Ignition energy (spark or heat)

20. Combustion Reactions In general: CxHy + O2  CO2 + H2O
Products in combustion are ALWAYS carbon dioxide and water. (although incomplete burning does cause some by-products like carbon monoxide)
Combustion is used to heat homes (Methane, CH4) and run automobiles (Octane, C8H18)

21. Combustion
Example
C5H O2  CO2 + H2O
Write the products and balance the following combustion reaction:
C10H O2  8 5 6

22. Mixed Practice
State the type, predict the products, check the charges and balance the following reactions:
BaCl2 + H2SO4 
C6H12 + O2 
Zn + CuSO4 
Cs + Br2 
FeCO3 

23. Solubility Table

24. Determining Reaction Types

25. Identifying Reactions and Predicting Products

26. Identifying Reactions and Predicting Products

27. Identifying Reactions and Predicting Products