1. Chemical Reactions

2. Describing Chemical Reactions
Chemical Reaction – process where a new substance is produced
Indications of a chemical reaction
heat and light
production of a gas
color change
formation of a precipitate
Precipitate – a solid formed when two ionic solutions are mixed

3. Types of Reactions
There are five types of chemical reactions we will talk about:
Combination
Decomposition
Single Replacement
Double Replacement
Combustion
You need to be able to identify the type of reaction and predict the product(s)

4. Combination Reactions
aka Synthesis reactions
occur when two or more substances combine and form a compound
Reactant + Reactant  1 Product
Ex: Ca (s) + Cl2 (g)  CaCl2 (s)

5. Practice
Predict the products. Write and balance the following synthesis reaction equations.
Example #1 - Aluminum metal reacts with fluorine gas
Al(s) F2(g)  2 3 2
AlF3 (s)

6. Decomposition Reactions
occurs when a compound breaks up into it’s elements when heated
1 Reactant  Product + Product
Ex: 2 KCl (s)  2K (s) + Cl2 (g)

7. Practice
Predict the products. Then, write and balance the following decomposition reaction equations:
Example #2 – Solid lead (IV) oxide decomposes using a catalyst
PbO2(s) 
Catalyst
Pb(s) + O2(g)

8. Single Replacement Reactions
occur when one element replaces another in a compound
a metal can replace a metal (+) OR a nonmetal can replace a nonmetal (-)
Ex: 2K (s) + MgCl2 (aq)  2 KCl (aq) + Mg (s)
Ex: Br2 (g) + 2 LiCl (aq)  2 LiBr (aq) + Cl2 (g)

9. Single Replacement Reactions
Write and balance the following single replacement reaction equation:
Example #3 - Zinc reacts with aqueous hydrogen monochloride
Zn(s) HCl(aq) 
Note: Zinc replaces the hydrogen ion in the reaction
Example #4 - Sodium chloride solid reacts with fluorine
NaCl(s) + F2(g)  2
ZnCl2(aq) + H2(g) 2 2
NaF(s) + Cl2(g)

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

11. Practice Predict the products. Balance the equation 3 2 6 3 3
Example # 5 – Aqueous calcium chloride reacts with aqueous sodium phosphate
CaCl2(aq) Na3PO4(aq) 
Example # 6 – Aqueous iron (III) chloride reacts with aqueous sodium hydroxide
FeCl3(aq) NaOH(aq)  3 2
Ca3(PO4)2 (aq) + NaCl(s) 6 3 3
Fe(OH)3 (aq) NaCl (s)

12. Combustion Reactions
occur when a hydrocarbon or alcohol reacts with oxygen gas
CxHy (or CxHyOH) + O2  CO2 + H2O
products are ALWAYS carbon dioxide and water
Ex : 2CH3OH + 3O2  4H2O + 2CO2

13. Combustion
Write the products and balance the following combustion reaction:
Example #7 -
C5H O2  8 6
H2O CO2 5

14. This is also called burning
This is also called burning!!! In order to burn something you need the 3 things in the “fire triangle”: 1) A Fuel (hydrocarbon) 2) Oxygen to burn it with 3) Something to ignite the reaction (spark)