1. Types of Chemical Reactions
Synthesis, Combustion, Decomposition and Replacement

2. You can think of atoms as people getting together as couples...
Analogy
Chemical Reaction
One person
An ion or element
A couple
A compound
Switching partners
A replacement reaction

3. The Get Together…

4. Synthesis

5. Decomposition

6. Decomposition

7. Single Replacement Reactions

8. Single Replacement Reactions

9. Double Replacement Reaction

10. Double Replacement Reaction

11. Combustion

12. Combustion

13. How does this analogy break down?
People in Relationships
Chemical Reactions
People can switch partners whenever they want
The ions or elements in a compound “switch partners” according to rules
We usually just think about one partner and one couple
In chemistry, we usually are dealing with billions of particles reacting at once
People don’t assume different states of matter
In double replacement reactions, there will be a change of state (a solid, liquid, or gas is formed)
People aren’t swimming in water
Displacement reactions generally happen in aqueous solutions

14. Let’s look at the reactions in more detail
Synthesis
Decomposition
Single-Replacement
Double-Replacement
Combustion

15. Combustion What are some types of combustion you are familiar with?
Every cell in your body is carrying out combustion

16. Combustion Oxygen combines with a metal, non-metal, or compound
Creates a metal oxide, non-metal oxide, or 2 or more oxides
Releases energy – heat, light
Can be a slower process too…

17. Synthesis
2 or more reactants combine to make a product A B AB

18. Decomposition
A compound breaks down into two or more substances

19. Single Replacement A metal replaces a hydrogen
A metal replaces another metal
We use an activity series to predict which metals are “stronger” and can knock out other metals from compounds

20. Activity Series
The most active metals are at the top. These will replace metals below them.
The halogens are also listed in order of most active at the top to least active at the bottom.
More active elements replace less active elements in single replacement reactions

21. Single Replacement Examples
2 AgNO3 + Cu  Cu(NO3) Ag
Fe + Cu(NO3)2   Fe(NO3)2 + Cu
Zn + 2HCL  ZnCl2 + H2

22. Double Replacement Reactions
Produces a precipitate, liquid or gas
All four of the ions switch partners
Aqueous solution

23. Double Replacement Examples
AgNO3(aq) + KCl(aq)  AgCl(s) + KNO3(aq)
CaCO3(aq) + 2 HCl(aq)  CaCl2(aq) + H2O(l) + CO2(g)
HCl(aq) + NaOH(aq)  HOH(l) + NaCl(aq)

25. How to identify a reaction
Steps to determine type of reaction
Write the chemical equation
Determine what is happening in the reaction
Use the table to identify the type of reaction
Check your answer by comparing the chemical equation to the generic equation
How to identify a reaction
Be systematic – it will help you identify the reaction type and the products!

26. How to identify a reaction
Example: Identifying a reaction
CaO (s) + CO2 (g)  CaCO3 (s)
2 compounds are reacting to form one compound
This is a synthesis reaction
A + B  AB
How to identify a reaction
Example:
Solid calcium oxide and carbon dioxide gas react to produce solid calcium carbonate

27. The main types of reactions Replacement Reactions: 2 types
Summary
The main types of reactions
Replacement Reactions: 2 types
Combustion – reaction with oxygen
Synthesis – two compounds or elements getting together
Decomposition – One compound splitting up
Replacement – Another ion moves in
Single replacement – a stronger cation steps in and replaces a weaker anion
Double replacement – 2 cations switch places, forming a precipitate, a liquid, or a gas

28. You try it! Work on these examples together in pairs.
Write the reaction
Balance the equation
Classify the reaction
Be prepared to present your results on the board!
Magnesium and Hydrochloric acid form Magnesium Chloride and Hydrogen
Carbon Dioxide and Water form Carbonic Acid (H2CO3)
Silver Nitrate and Sodium Chloride form Silver Chloride and Sodium Nitrate
Heating sodium bicarbonate (NaHCO3) releases water and carbon dioxide and sodium carbonate

29. You try it!
Magnesium and Hydrochloric acid form Magnesium Chloride and Hydrogen:
Mg + HCl  MgCl + H2 (skeleton equation)
2Mg + 2HCl  2MgCl + H2 (balanced equation)
Single replacement (reaction type)
Carbon Dioxide and Water form Carbonic Acid (H2CO3):
CO2 + H2O  H2CO3 (skeleton equation)
CO2 + H2O  H2CO3 (it’s already balanced!)
Synthesis (reaction type)

30. You try it!
Silver Nitrate and Sodium Chloride form Silver Chloride and Sodium Nitrate
AgNO3 + NaCl  AgCl + NaNO3 (skeleton equation)
AgNO3 + NaCl  AgCl + NaNO3 (already balanced)
Double replacement (reaction type)
Heating sodium bicarbonate releases water and carbon dioxide and sodium carbonate
NaHCO3  Na2CO3 + H2O + CO2 (skeleton equation)
2NaHCO3  Na2CO3 + H2O + CO2 (balanced equation)
Decomposition (reaction type)