1. Chemical Equations & Reactions(Rxn’s)
Chapter 8
Chemical Equations
&
Reactions(Rxn’s)

2. Chemical Reactions(Rxn’s)
Chemical Reaction: the process in which one or more substances is changed into one or more different substances
Chemical Equation: Reactants  Products
Chemical equations use symbols & formulas to identify the amount and type of chemical reactants & products in a reaction
Ex: C6H12O6(s) + 6O2(g)  6 H2O(l) + 6 CO2(g)
State of Compound
# of Molecules

3. Characteristics of Chemical Reactions
1) A chemical equation must represent all reactants and products
2) A chemical equation must contain correct formulas for reactants and products
3) Conservation of mass must be expressed in the equation

4. Indicators of Chemical Reactions
Evolution(giveing off) of light and heat
Production of gas (bubbling)
Formation of a Precipitate
(liquid + liquid  solid)
Color change

5. Significance of Chemical Reactions
Coefficients indicate relative amounts of reactants and products
Ex: H2 + Cl2  2HCl
* Coefficients indicate mole ratio
1 Mole
1 Mole
2 Moles

6. Symbols Used in Chemical Reactions

7. More Symbols

8. Types of Equations
Word Equations- use molecular names of reactants and products
Ex: methane gas + oxygen gas yields carbon dioxide gas and liquid water
Formula Equations- use chemical formulas to represent reactants and products
Ex: CH4(g) + 2O2(g)  CO2(g) + 2H2O(l)

9. Balancing Equations
A balanced equation has an equal # of all atoms on both sides of the chemical equation
Ex: __C2H4 + __O2  __CO2 + __H2O

10. Types of Chemical Reactions
Synthesis Reaction: 2 or more substances combine to form 1 new compound (A + X  AX)
Ex: 2Mg(s) + O2(g)  2MgO(s)
Decomposition Reaction: 1 substance breaks down into 2 new substances (AX  A + X)
Ex: CaCO3(s)  CaO(s) + CO2(g)

11. Reaction Types
Single-Replacement Reaction: one element replaces a similar element in a compound (A + BX  AX + B)
Ex: 2Al + 3Pb(NO3)2  3Pb + 2Al(NO3)3
Double-Replacement Reaction: ions of 2 compounds exchange places in an aqueous solution (AX + BY  AY + BX)
Ex: 2KI + Pb(NO3)2  PbI2 + 2KNO3

12. Reaction Types
Combustion Reaction- a fuel / hydrocarbon) combined with oxygen produces carbon dioxide and water
Ex: C3H8 + 5 O2  3 CO2 + 4 H2O
Fuel
Oxygen
Carbon Dioxide
Water

13. Determining Reaction Types

14. Activity Series of Elements
The activity series is a list of elements organized according to the ease with which the elements undergo certain single-replacement reactions
Listing shows elements from most active to least active
Used to predict whether a reaction will or will not occur

15. Activity Series

16. Activity Series Examples
Ex: __ Al + __ ZnCl2 
__ Co + __NaCl 

17. Specific Examples of Reaction Types

18. Synthesis (A + X  AX) Oxygen and Sulfur ex: 2Mg + O2  2MgO
b) Metal and Halogens
ex: 2Na + Cl2  2NaCl
c) Oxides
ex: CaO + H2O  Ca(OH)2

19. Decomposition (AX  A + X)
a) Binary Compounds ex: 2HgO  2Hg + O2
b) Metal Carbonates ex: CaCO3  CaO + CO2
c) Metal Hydroxides ex: Ca(OH)2  CaO + H2O
d) Metal Chlorates ex: 2KClO3  2KCl + 3O2
e) Acids ex: H2SO4  SO3 + H2O

20. Single Replacement (A + BX  AX + B)
Metal replaced by metal
ex: 2Al + 3Pb(NO3)2  3Pb + 2Al(NO3)3
b) Hydrogen replaced by metal
ex: 3Fe + 4H2O  Fe3O4 + 4H2
c) Acid Hydrogen replaced by metal
ex: Mg + 2HCl  H2 + MgCl2
d) Replacement of halogens
ex: Cl2 + 2KBr  2KCl + Br2

21. Double Replacement (AX + BY  BX +AY)
Formation of a precipitate
ex: 2KI + Pb(NO3)2  PbI2 + 2KNO3
b) Formation of gas
ex: FeS + 2HCl  H2S + FeCl2
c) Formation of water
ex: HCl + NaOH  NaCl + H2O

22. Combustion (Fuel + O2  H2O + CO2)
Hydrogen combustion
ex: 2H2 + O2  2H2O
b) Organic combustion
ex: C3H8 + 5O2  3CO2 + 4H2O

23. END OF CHAPTER 8 NOTES!!!