1. Synthesis and Decomposition Reactions
SNC2P

2. Chemical Change
There are 6 clues that enable you to identify if a chemical reaction has occured.
Formation of gas
Formation of precipitate
Change in colour
Change in odour
Change in temperature
Production of light

3. Can you identify the chemical changes occuring in each picture?

4. Classifying Chemical Reactions
Depending on the reaction that occurs different products will form.
There are 5 main types of chemical reactions:
1) Synthesis
2) Decomposition
3) Single Displacement
4) Double Displacement
5) Neutralization Reaction

5. Synthesis Reactions
A chemical reactions whereby two or more reactants combine to form a product.
Two reactants (A and B) have reacted to form one product (AB)
A compound always forms

6. The “Haber” process to produce ammonia
Ex. Haber Process
NH3 is an important product made in synthesis reactions.
NH3 is formed when the elements Nitrogen and Hydrogen combine.
This chemical reaction was discovered by Fritz Haber a German chemist.
This reaction occurs under high pressure and temperature.
The “Haber” process to produce ammonia
N2(g) + 3H2(g) NH3(g)

7. The shuttle “blast off”
Ex. Space Shuttle
The synthesis reaction between liquid hydrogen and liquid oxygen produces the product required to launch the space shuttle.
Remember!! Hydrogen and oxygen are diatomic molecules. This must be considered when balancing your equation.
The shuttle “blast off”
2H2(l) + O2(l) H2O(g)

8. Ex. Atmospheric Pollutants
Many elements found in the atmosphere can react to form products involved in atmospheric pollution.
The production of “smog”
N2(g) + O2(g) NO2(g)
and
2NO(g) + O2(g) NO2(g)
Oxygen gas can react with nitrogen gas to form a variety of nitrogen oxides.

9. Synthesis Reactions
Complete the following synthesis reaction:
Na (s) Cl (g) NaCl (s)
Step 1: Both elements must combine to form the product. Write their chemical charges.
Step 2: Use the cross-over method to determine the chemical formula of the product.

10. Synthesis Reaction
Step 3: Write out the skeleton equation of the reaction.
Na (s) Cl2 (g) NaCl (s)
Step 4: Balance the chemical equation.
2 Na (s) Cl2(g) NaCl (s)
Make sure to always check that the amount of elements in your products are equivalent to the amount of elements in your reactants.

11. Let’s Practice ! Complete the following equations. Ca (s) + N2 (g)
K (s) + O 2 (g)
Cs (s) + P4 (s)
Al (s) + F2 (g)

12. Decomposition Reactions
A decomposition reaction is a chemical reaction in which a compound breaks down (decomposes) into two or more simpler compounds or elements.
The charges are transferred back to the metals during a decomposition reaction.
The reactants are always compounds. The products can be a combination of compounds and elements.

13. The electrolysis of water
Ex. Hydrogen Fuel
The decomposition of water (H2O ) can produce Hydrogen gas.
The process of electrolysis enables this decomposition reaction to occur.
The electrolysis of water
2H2O(l) H2(g) + O2(g)

14. Decomposition of sodium azide
Ex. Airbag
The decomposition of sodium azide enables the airbag to inflate.
The nitrogen gas that is produced inflates the bag.
Decomposition of sodium azide
2NaN3(s) N2(g) + 2Na(s)

15. Decomposition Reactions
Complete the following decomposition reaction:
AgCl (s) Ag (s) + Cl2 (g)
Step 1: The reactant must decompose into two reactants. Separate the two elements in the reactants.
Step 2: Idenfity the state of each element and whether or not it is a diatomic molecule.

16. Decomposition Reaction
Step 4: Write out the skeleton equation of the reaction.
AgCl (s) Ag (s) Cl2 (g)
Step 5: Balance the chemical equation.
2 AgCl ( s ) Ag (s) + Cl2 (g)
Make sure to always check that the amount of elements in your products are equivalent to the amount of elements in your reactants.

17. Let’s Practice!
AuCl3 (s)
MgF2 (s)
Li2O (s)
CsCl (s)