1. Precipitation Reactions

2. Don’t write - Chemical Equations
Chemical Reaction = new substance is produced.
Reactants (R) – left of arrow
Products (P) – right of arrow

3. Don’t Write - Indications of a Chemical Reaction
Evolution of heat/light
Exothermic (releases heat)
Endothermic (absorbs heat)
Production of a gas
Formation of a precipitate (solid)
Color change

4. Vocabulary to Know Soluble – will dissolve (aq)
Insoluble – will not dissolve (s)
Examples: Sand ???
Sugar ???
Salt ???
Dirt ???

5. Aqueous Solution – homogeneous mixture of a soluble compound dissolved in water
Precipitate – a solid formed in solution
Cation – positive ion (written first in a compound)
Anion – negative ion (written last in a compound)

6. Precipitation Reaction
(also called):
*Double Replacement
*Ion switch
Ions of 2 aqueous reactants exchange places and form 2 new products
(need volunteers)

7. Symbols used in Equations
 - yields (=)
The following are written to the right of the compound in a reaction:
(g) – gas CO2 (g)
(s) – solid
(l) – liquid
(aq) – aqueous (dissolved in water)

8. One product will be soluble (aq) (dissolved in water – liquid).
One product will be insoluble (s) - exist as a solid (it will precipitate out of solution)

9. Soluble or Insoluble??
Check the solubility of common ionic compounds on reference materials sheet
Indicate which product is soluble and which is insoluble!!!!!

10. Precipitation reactions - YouTube
Double Replacement - Production of Precipitate
Orange tornado – YouTube

11. Are these compounds soluble or insoluble? (soluble =aq, insoluble = s)
K2SO4
2. AgCl
CaI2
4. K3PO4

12. Always Soluble
Usually Soluble
Usually Insoluble

13. Precipitation examples
1. Zinc nitrate(aq) + ammonium sulfide(aq)→ ?
2. Calcium hydroxide(aq) + ammonium sulfate (aq)→

14. Acid-Base Reactions Neutralization

15. Acid – Begins with hydrogen (H).
*HCl
*HNO3
Base – Has a hydroxide (OH)
*LiOH
*Ca(OH)2
Salt – An ionic compound
*NaCl
*NH4PO4

16. Acid Base Reaction Acid and base reacts to form WATER and a SALT.
- Balance the charges of the salt (+ comes from the base and neg comes from the acid)

17. Balance salts and then entire equation
Example
H3PO LiOH →

18. Fe(OH) HBr →

19. H2CO Ca(OH)2 →

20. What reaction will produce the salt K2SO4

21. Reduction – Oxidation Reactions (Redox)

22. Involves a transfer of electrons (gaining and losing).
Reaction will have a free element.

23. Example 2 Na + Cl2 → 2 NaCl (Na is not gaining → (Na loses 1 e-)
or losing e-)
This is a redox reaction because Sodium has to lose electrons to bond with chlorine.
And… chlorine gains electrons to bond with sodium.

24. Assigning oxidation numbers:
1. THE SUM OF OXIDATION NUMBERS (states) IN A COMPOUND WILL EQUAL ZERO.
2. Uncombined elements are 0 (zero).
example: Cu O2 S8
3. Hydrogen and group I = + 1
4. Group II = +2
5. Oxygen = -2
6. Fluorine = -1

27. Examples:

28. Compare oxidation states from reactant to product:
**Increases (loses electrons) – Oxidized
**Decreases (gains electrons) – Reduced
_________|_________
Reduced Oxidized

29. Examples:

30. Non-Example
HCl + NaOH → NaCl + H2O (Na loses 1 e-) (Na loses 1 e-) Acid-Base and Precipitation reactions are NOT redox because the charge (oxidation state), on the product side is the same as the reactant side.

31. 1. Redox reactions (reduction-oxidation)
1. Redox reactions (reduction-oxidation) *Has a “free element” A + BC → B + AC AB → A + B A + B → AB

32. 2. Neutralization Reactions (Acid-Base)
*Reactants are an acid – (Starts with H), and a base (ends with OH - hydroxide) *Always produces water. H A + B OH → BA + H2O

33. 3. Precipitation reactions (ion switch)
*Has two compounds reacting (no free elements). *Forms a solid product (precipitate) AB + CD → AD + CB

34. Note to self – add reagents and assigning oxidation states and number line.