1. Chapter 11
Chemical Reactions

2. Note Taking Tips! Paraphrase, paraphrase, paraphrase!
Use symbols, arrows, pictures, and abbreviations whenever possible.
Write side notes to help you remember concepts.

3. Chemical Reactions Occur every minute of every day!
When one or more reactants change into one or more products.

4. Fe + O2 Fe2O3 Chemical reactions are described by chemical equations.
Skeleton Equation: chem equation that doesn’t indicate relative amounts of reactants and products.
Chemical Equation: describe chemical reactions.
Fe + O2 Fe2O3
Reactants Products
It needs to be balanced!!!

5. Draw this one

6. Catalyst: a substance that speeds up the reaction but is not used up in a reaction.
Neither a reactant nor a product
Written above arrow in chem equation.
MnO2
H2O2(aq) H20(l) + O2(g)

7. Balancing Chemical Equations
A chemical reaction where each side of the equation has the same number of atoms of each element and mass is conserved.
Fe + O2 > Fe2O3

8. Steps to Balancing
1. Count atoms on each side. Count polyatomic ion as one unit if it appears unchanged on right.
2. Balance elements one at a time using coefficients
Balance elements that appear only once 1st
Never change subscripts
3. Check work and make sure all coefficients are in lowest possible ratio.
H O2 > H2O

9. Let’s try some!

11. Let’s try some! _____ S + _____ O2 --> _____ SO2
_____ Na + _____ O2 --> _____ Na2O2
3. _____ Hg + _____ O2 --> _____ HgO
4. _____ Ag2O --> _____ Ag + _____ O2
5. _____ Ba(OH)2 + _____ H3PO4 --> _____ BaHPO4 + _____ H2O
Hint: Do Hydrogen last

12. Let’s try some!

13. Practice

14. Practice

15. Your Task

16. 11.2 Types of Chemical Reactions
5 general types
Combination
Decomposition
Single-replacement
Double-replacement
Combustion

17. Combination
A reaction in which two reactants combine to form one product.
R+S RS
Example: Rust
4 Fe + 3 O Fe2O3
Reaction of elements with oxygen and sulfur
Reactions of metals with Halogens
Synthesis Reactions with Oxides
There are others not covered here!

18. Decomposition
Reaction in which one compound breaks down (or decomposes) to form two or more simpler products.
RS R+S
Example: Decomposing Aluminum Oxide to make Aluminum and Oxygen
2 Al2O3 4 Al2 + 3 O2

19. Decomposition continued
Decomposition of:
Binary compounds H2O(l )  2H2(g) + O2(g)
Metal carbonates CaCO3(s)  CaO(s) + CO2(g)
Metal hydroxides Ca(OH)2(s)  CaO(s) + H2O(g)
Metal chlorates KClO3(s)  2KCl(s) + 3O2(g)
Oxyacids H2CO3(aq)  CO2(g) + H2O(l )

20. Single-Replacement
An element reacts with a compound to form a new compound and release a different element.
T+RS TS+R
Example: Pure silicon for computer chips.
SiCl4 + 2H2 Si + 4 HCl
Metals by another metal
Hydrogen in water by a metal
Hydrogen in an acid by a metal
Halogens by more active halogens

21. The Activity Series of Metals
Lithium
Potassium
Calcium
Sodium
Magnesium
Aluminum
Zinc
Chromium
Iron
Nickel
Lead
Hydrogen
Bismuth
Copper
Mercury
Silver
Platinum
Gold
Metals can replace other metals provided that they are above the metal that they are trying to replace
Metals above hydrogen can replace hydrogen in acids.
Metals from sodium upward can replace hydrogen in water

22. Double-Replacement
The ions of two compounds exchange places in an aqueous solution to form two new compounds.
R+S- + T+U- R+ + U- + T+S-
Example: One of the compounds formed is usually a precipitate, an insoluble gas that bubbles out of solution, or a molecular compound, usually water.

23. Combustion
A substance combines with oxygen, releasing a large amount of energy in the form of light and heat.
Example: Reactive elements combine with oxygen.
The burning of natural gas, wood, gasoline
P4(s) + 5O2(g)  P4O10(s)
(This is also a synthesis reaction)
C3H8(g) + 5O2(g)  3CO2(g) + 4H2O(g)

24. How to identify the type of reaction
Does your reaction have oxygen as one of it's reactants and carbon dioxide and water as products?
If yes, then it's a combustion reaction.
Does your reaction have two (or more) chemicals combining to form one chemical?
If yes, then it's a synthesis reaction.
Does your reaction have one large molecule falling apart to make several small ones?
If yes, then it's a decomposition reaction.
Does your reaction have any molecules that contain only 1 element?
If yes, then it's a single displacement reaction.
If you haven't answered "yes" to any of the questions above, then you've got a double displacement reaction.

25. Practice!

26. Practice!