1. Classifying Equations
Chemical Reactions
Writing Equations
Balancing Equations
Classifying Equations
Predicting Products

2. Writing Equations
Chemical equations represent changes that occur in a chemical reaction.
Reactants – starting substances
Always on the left of the arrow
Products – substances formed in a reaction
Always on the right of the arrow
 means “yields” “forms” “produces”

3. Example:
Yields or makes
NaCl + AgBr  NaBr + AgCl
Reactants
Products

4. State Symbols cr – crystalline solid s - solid g – gas l – liquid
aq – aqueous solution

5. 2H2(g) + O2(g)  2H2O(l)
Mg (s) + 2HCl (aq)  MgCl2 (aq) + H2 (g)

6. Writing and Balancing Equations
Determine reactants and products.
Write correct formulas for each.
Add coefficients to balance.
the number of atoms of each element must be equal on each side of the equation.
Law of Conservation of Matter
YOU CANNOT EVER CHANGE SUBSCRIPTS! TO BALANCE EQUATIONS, YOU CAN ONLY ADD COEFFICIENTS!!!!

7. When zinc reacts with hydrochloric acid, zinc chloride and hydrogen are formed.

8. When propane burns in oxygen, carbon dioxide and water are formed.
C3H8 + O2
CO2 +
H2O

9. Classifying Chemical Reactions
Single Displacement
One element replaces another in a compound
A + BC  AC + B
Element + Compounds  Element + Compound
+ ions replace + ions, – ions replace – ions

10. Single Replacement 2Ag + ZnCl2  2AgCl + Zn F2 + 2 NaCl  Cl2 + 2 NaF
+ ion replaces + ion
F NaCl  Cl NaF
- ion replaces - ion

11. 2. Double Displacement: Two compounds swap ions AB + CD  AD + CB
Compound + Compound  Compound + Compound

12. Double Displacement ZnI2 + CuS  ZnS + CuI2 NaOH + HCl  NaCl + HOH -

13. Activity Series of Metals
Lithium Potassium Calcium Sodium Magnesium Aluminum Zinc Chromium Iron Nickel Lead Hydrogen Bismuth Copper Mercury Silver Platinum Gold
*Metals above other metals will replace them in replacement reactions.
2Fe (s) + Pb(SO4)2(aq) + 2Fe(SO4)(aq) + Pb(s)
*All metals above H will replace H in acids.
2Al(s) + 6HCl(aq) → 2AlCl3(aq) + 3H2(g)
*All metals above Na will replace H in water.
Ca(s) + H2O → CaO(aq) + H2(g)

14. Activity Series for Halogens
REMEMBER: Halogens are elements in Group 17
Elements above others will replace them.
Cl2(g) + 2NaI(aq) → 2NaCl(aq) + I2(g)

15. 3. Decomposition
1 reactant breaks down to form several products (may be elements or compounds)
ABC  A + BC
C  E + E or E + C or C + C
Example:
2 KClO3  2 KCl O2

16. Decomposition Rules: 2MgO  2Mg + O2 Mg(OH)2  MgO + H2O
Metallic oxides form metals and oxygen.
2MgO  2Mg O2
Metallic hydroxides form metallic oxides and water.
Mg(OH)2  MgO + H2O
Metallic carbonates form metallic oxides and carbon dioxide.
MgCO3  MgO + CO2

17. Metallic chlorates form metallic chlorides and oxygen.
Mg(ClO3)2  MgCl2 + 3O2
Oxyacids form nonmetallic oxides and water.
H2CO3  CO H2O
Compounds decomposed by electrolysis form elements.
2NaCl  2Na + Cl2

18. 4. Synthesis: 2 or more substances combine to form 1 new substance
A + B  AB or AB + C  ABC
E + E  C or C + E  C
Opposite of decomposition meaning more than 1 reactant join to form 1 product

19. Synthesis
N2 + 3 H2  2 NH3
1 product
NH3 + HCl  NH4Cl

20. 5. Combustion CnH(2n+2) + O2  CO2 + H2O
A hydrocarbon reacts with oxygen to form carbon dioxide and water
CnH(2n+2) + O2  CO2 + H2O

21. Combustion CH4 + O2  CO2 + H2O C8H18 + O2  CO2 + H2O
Let’s balance these!
CH4 + O2  CO2 + H2O
C8H18 + O2  CO2 + H2O

22. Balance Equations and ID Rxn Type
H2S + O2 → H2O + S Cu(NO3)2 + NH4(OH) → Cu(OH)2 + NH4(NO3) NH3 + O2 → N2 + H2O Hg2O + O2 → HgO

23. Balance Equations and ID Rxn Type
C4H10 + O2 → CO2 + H2O H2O → H2 + O2 Ba(NO3)2 + Na2(CrO4) → Ba(CrO4) + Na(NO3)

24. Predicting Products
aluminum plus hydrochloric acid calcium hydroxide plus nitric acid zinc chloride plus hydrogen sulfide

25. Predicting Products
sodium chlorate (heated) barium nitrate plus sodium chromate