1. Types of Reactions

2. What is a chemical reaction -
1. A block of ice melting?
Physical – no change in chemical composition
2. A block of dry ice converting to CO2 (g)
Physical – no change in chemical composition – same as ice melting
3. A log burning in a fire place
Combustion reaction – What kinds of changes do we see?
4. Cement hardening after being poured
Hydration reaction – it does not “dry” out but changes chemical form
5. Fire works exploding.
Combustion and many, many other reactions

3. Evidence of Chemical Reactions
Color Change
Formation of a solid in a clear solution
Precipitate
Evolution (formation) of a gas – such as CO2
Creation or absorption of heat
Temperature change in the absence of a heat source
Some evidence of chemical reactions can only be discovered by a detailed chemical analysis.

4. Types of Basic Chemical Reactions
The Reactions
Synthesis (combination)
Decomposition
Single replacement (single displacement)
Double replacement (double displacement)

5. Types of Basic Chemical Reactions
The Reactions - Continued
Acid-base
(neutralization)
Precipitate
Oxidation-reduction
(redox)

6. Synthesis
Definition - A reaction in which a new compound is formed from a reaction of two less complex reactants. A B A B

7. Example – Synthesis Reaction
Fe + S8 →
Fe + S8 → FeS
8 Fe + S8 → 8 FeS

8. Example- “Complex” Synthesis Reaction
CO2 + H2O →
CO2 + H2O → C6H12O6 + O2
6 CO2 + 6 H2O → C6H12O6 + 6O2

9. Decomposition
A reaction where a substance is broken down into simpler substances. A B A B

10. Example – Decomposition
H2O2 →
H2O2 → H2O + O2
2 H2O2 → 2 H2O + O2

11. Example - Decomposition
Ag2O (s) →
Ag2O (s) → Ag (s) + O2
2 Ag2O (s) → 4 Ag (s) + O2

12. A A B B C C A A B C Single Replacement
A chemical reaction where an element reacts with a compound and takes the place of another element in the compound.
This is easily seen when an element reacts with a compound. A A B B C C A A B C

13. Example - Single Replacement
Zn(s) + HCl(aq) →
Zn(s) + HCl(aq) → ZnCl2(aq) + H2(g)
Zn(s) + 2 HCl(aq) → ZnCl2(aq) + H2(g)

14. Example - Single Replacement
Fe2O3 (s) + C (s) →
Fe2O3 (s) + C (s) → Fe(s) + CO2 (g)
2 Fe2O3 (s) + 3 C (s) → Fe(s) + CO2 (g)

15. B C A D Double Replacement
When two compounds react and swap elements forming two new compounds.
This is easily seen when two compounds react with each other. Normally occurs between ionic compounds; but not always. B C A D

16. Example - Double Replacement
Zn(s) +AgNO3 + NaCl →
Zn(s) +AgNO3 + NaCl → AgCl + NaNO3
Already Balanced

17. Example - Double Replacement
BaCl2(aq) + Na2SO4(aq) →
BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + NaCl(aq)
BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + 2 NaCl(aq)

18. Neutralization Reaction (Acid-Base Reactions)
Acids – a chemical that donates (gives away) hydrogen ions and accepts electrons.
H+ ions are simply a single protron.
When added to water acids normally disassociate (break up) into a cation (H+) and an anion.

19. Neutralization Reaction (Acid-Base Reactions)
The word “acid” comes from the latin word acidus meaning sour.
This is due to the sour taste of lemon juice (citric acid) and vinegar (acetic acid).

20. Neutralization Reaction (Acid-Base Reactions)
Acids tend to dissolve in water.
The stronger the acid the more completely it dissolves such as HCl – Hydrochloric Acid Cl H
Cl+ H+

21. Neutralization Reaction (Acid-Base Reactions)
Bases – Bases are chemicals that tend to donate electrons or hydronium ions (H3O+).
A common base is sodium Hydroxide NaOH

22. Neutralization Reaction (Acid-Base Reactions)
When strong acids and bases react you are left with a salt and water. O H H+ A B O H A B

23. Neutralization Reaction (Acid-Base Reactions)
The reaction of Hydrochloric Acid and Sodium Hydroxide shows this
HCL + NaOH  NaCl + H2O O H H Cl Na O H Na Cl

24. Neutralization Reaction (Acid-Base Reactions)
There are other acid-base reactions that are not as straight forward. These tend to not balance on the Ph Scale to a fully neutral solution.
Weak Acid – Strong Base
Strong Acid – Weak Base
Weak Acid – Weak Base