1. Chemical Equations & Reactions (Rxns)
Chapter 8
Chemical Equations
&
Reactions (Rxns)

2. Chemical Reactions (Rxns)
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 (emitting) 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. __ Mg + __ Cl  __ MgCl2

10. Balancing Equations Balance each type of atom one at a time.
Balance atoms that appear once on each side first.
Treat polyatomic ions as one entity.
Balance hydrogen & oxygen atoms last.
Count your atoms to be sure the equation is balanced.
If the coefficients have a GCF, divide!

11. Balancing Equations – Practice!
Ex:
__C2H4 + __O2  __CO2 + __H2O
__ Na3PO4 + __ KOH __ NaOH + __ K3PO4

12. 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)

13. 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

14. 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

15. Determining Reaction Types

16. 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

17. Activity Series

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

19. END OF CHAPTER 8 NOTES!!!