1. Classifying chemical reactions
Advanced Chemistry

2. Driving Force 3 – Formation of a Gas
Double replacement reactions may also form a gaseous product
Physically leaves and prevents reformation of reactants
Very strong driving force

3. Compounds that Tend to Form Gases
If you see the following substances in a reaction, realize that they will break up into gases and leave
These compounds are formed from acids with carbonates, sulfites, sulfides, nitrites, and bases with ammonium compounds
Watch For…
It Turns Into…
H2CO3
→ CO2 (g) + H2O
H2SO3
→ SO2 (g) + H2O
H2S
→ H2S (g) [rotten egg smell]
NH4OH
→ NH3 + H2O
2HNO2
→ NO (g) + NO2 (g) + H2O

4. Driving Force 4 – Transfer of Electrons
Occurs between a metal and a non-metal
Forms an ionic compound
Metal transfers electrons to the non-metal
Metal becomes a cation and non-metal becomes an anion
Called an oxidation-reduction reaction (REDOX)
Oxidation
Loss of electrons
Reduction
Gain of electrons
LEO GER
OIL RIG

5. Oxidation Losing Electrons is Oxidation (LEO) Al → Al3+ + 3e-
Mg → Mg2+ + 2e-

6. Reduction Gaining Electrons is Reduction (GER) Fe3+ + 3e- → Fe
Cl + e- → Cl-

7. Oxidation-Reduction Mneumonic

8. Summary of Oxidation-Reduction Reaction

9. Practice, Practice, Practice
2Cs(s) + F2(g) → 2CsF(s)
Ions present in CsF?
Which element is oxidized?
Which element is reduced?
2Na(s) + Br2(l) → 2NaBr(s)
Ions Present:
Oxidation:
Reduction:
2Ca(s) + O2(g) → 2CaO(s)

10. Transfer of Electrons Visual

11. Driving Forces of Chemical Reactions
Remember:
Chemical changes are a result of chemical reactions
Chemical reactions involve a change in energy
Two compounds will react if there is at least one driving force present:
Formation of a solid (precipitate)
Formation of water
Transfer of electrons
Formation of a gas
But there’s so many compounds and so many reactions! How can I possibly know them all??

12. Why Classify Chemical Reactions?
There are MILLIONS of chemical reactions that occur in the world
By classifying the type of chemical reaction, reactions become easier to understand
One popular classification scheme breaks up the types of chemical reactions into six different categories:
Double Replacement
Acid-Base Neutralization
Synthesis
Decomposition
Combustion
Single Replacement

13. Double Displacement Reactions
Anions and cations of two different molecules switch places
Form entirely different compounds
Driving forces observed:
Formation of a solid
Formation of a gas
General form:
AB + CD→AD + CB

14. Double Replacement Reactions
Assume each reactant is aqueous
Need to use solubility rules to determine if a solid forms
If a solid does form, reaction can be written as a net ionic equation eliminating the spectator ions that remain unchanged during the reaction
Example:
Reaction of lead (II) nitrate with potassium iodide to form lead (II) iodide and potassium nitrate
𝑃𝑏 𝑁 𝑂 𝐾𝐼→ 𝑃𝑏𝐼 2 +2𝐾𝑁 𝑂 3

15. Acid-Base Neutralization Reactions
Special kind of double displacement reaction
Takes place when a strong acid and strong base react with each other
Driving forces observed:
Formation of water
H+ ion in the acid reacts with the OH- ion in the base
Products formed are water and some ionic salt
General form:
HA + BOH → BA + HOH (H2O)
Example:
Reaction of hydrobromic acid with sodium hydroxide
𝐻𝐵𝑟+𝑁𝑎𝑂𝐻→𝑁𝑎𝐵𝑟+ 𝐻 2 𝑂

16. Reaction of iron and sulfur to form iron (II) sulfide
Synthesis Reactions
Two or more simple compounds combine to form a more complicated one
Driving forces observed:
Transfer of electrons
General form
A + B→AB or AB + C → ABC
Example:
Reaction of iron and sulfur to form iron (II) sulfide
8 𝐹𝑒+ 𝑆 8 →8 𝐹𝑒𝑆

17. Decomposition Reactions
Opposite of a synthesis reaction
A complex molecule breaks down to make simpler ones
Driving forces observed:
Transfer of electrons
Formation of a gas
General form:
AB → A + B or ABC → AB + C
Example:
Electrolysis of water to make oxygen and hydrogen gas
(Electricity is applied to break up the water into its components)
2 𝐻 2 𝑂→ 2𝐻 2 + 𝑂 2

18. Some Decomposition Rules
Compound
Decomposition Products
Carbonates
(HCO3-, CO3 2-)
CO2 + Metal Oxide
[Metal oxide can be H2O]
Hydroxides
(OH-)
H2O and Metal Oxide
Chlorates
(ClO4-, ClO3-, ClO2-, ClO-)
O2 and Metal Chloride
Oxides
O2 and Metal

19. Combustion Reactions
Oxygen combines with a hydrocarbon (compound that contains only carbon and hydrogen) to form water and carbon dioxide
Reactions produce heat
Exothermic
Driving forces observed:
Formation of a gas
Formation of water
General form:
CxHy + O2 → CO2 (g) + H2O (g)
Example
Burning of napthalene
𝐶 10 𝐻 𝑂 2 →10 𝐶𝑂 𝐻 2 𝑂

20. Single Displacement Reactions
One element trades places with another element in a compound
Driving forces observed:
Transfer of electrons
General form:
A + BC → AC + B or A + BC → BA + C
Example
Magnesium replaces hydrogen in water to make magnesium hydroxide and hydrogen gas
𝑀𝑔+2 𝐻 2 𝑂→𝑀𝑔( 𝑂𝐻) 2 + 𝐻 2

21. Metals and Non-metals Reactivity
Not all elements are equal in their ability to replace other elements
Metals, such as lithium, sodium, potassium, strontium and calcium are referred to as “very active” metals due to the fact that they give up electrons very easily
Other metals are “less active”
Non-metals also vary in their reactivities
In order to predict products of single replacement reactions or to predict if they will occur at all, an activity series is used
New pink sheet!

22. A Handy Checklist for Classifying Type of Reactions
Follow this series of questions
When you answer “yes” to a question, stop!
Does your reaction have oxygen as one of its 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 one element?
If yes, then it’s a single displacement reaction
Does your reaction have water as one of the products?
If yes, then it’s an acid-base reaction!
If you haven’t answered “yes” to any of the questions above, then you’ve got a double displacement reaction!