1. Unit #8 Chemical Reactions
Part 2
Predicting Products

2. Review
A chemical reaction is the rearrangement of atoms to form new substance(s). Reactant(s) appear on the left, and product(s) appear on the right.
reactants product
Example: 2 H2 + O2  2 H2O
When we look at any chemical reaction, in order for it to be accurate, it must show that the law of conservation of mass is obeyed.

3. Law of Conservation of Mass
mass is neither created nor destroyed in a chemical reaction
total mass stays the same
atoms can only rearrange
So, we need to make sure that there are the same number of each type of atom on each side of the chemical equation.
To do this, we add coefficients in front of the compounds until these atoms are “balanced.”

4. Refresh your memory by balancing these equations:
__MgCl2 +__NaOH  __Mg(OH)2 +__NaCl
__Fe2(SO4)3 +__KOH  __K2SO4 +__Fe(OH)3 2 2 6 3 2

5. Synthesis
2 or more elements/compounds combine to form 1 product.
Only one product!
Analogy: Mixing 2 or more ingredients together to get 1 cake. .
A + B  AB

6. Must crisscross to get new compound!
Synthesis
Example: 2 Mg + O2  2 MgO
Must crisscross to get new compound!
Al(s)+ Cl2(g) 
AlCl3(s)

7. Na + F2  Na F BALANCE Na + F2  NaF Practice Problems: Na + F2 
B N2  +1 -1
Na + F2  Na F
BALANCE
Na + F2  NaF 2 2

8. B + N2  B N BALANCE B + N2  BN Practice Problems: Na + F2  B + N2 +3 -3
B + N2  B N
BALANCE
B + N2  BN 2 2

9. Decomposition
1 compound is broken down into 2 or more simpler elements/compounds.
only one reactant
Analogy: A couple breaks up. Or a body decompses.
AB  A + B

10. Decomposition
Example
Diatomic
KBr 
K Br2

11. Any Diatomic atoms? Na2O  Na O BALANCE Na2O  Na + O2
Practice Problems:
Na2O 
Any Diatomic atoms?
Na2O  Na O + 2
BALANCE
Na2O  Na + O2 2 4

12. A + BC  B + AC Single Replacement
one element replaces another in a compound
metal replaces metal (+)
nonmetal replaces nonmetal (-)
A + BC  B + AC

13. Fe(s)+ CuSO4(aq)  Cu(s)+ FeSO4(aq) Br2(l)+ NaCl(aq)  N.R. Products:
Metal replacement:
2 Na + CuCl2  2 NaCl + Cu
Halogen replacement:
F KCl  2 KF + Cl2
free element must be more active (check activity series)
Fe(s)+ CuSO4(aq) 
Cu(s)+ FeSO4(aq)
Br2(l)+ NaCl(aq) 
N.R.

14. Metals Nonmetals lithium fluorine potassium chlorine calcium bromine
Activity Series
Activity Series
Metals
Nonmetals
lithium
fluorine
potassium
chlorine
calcium
bromine
sodium
iodine
magnesium
oxygen
aluminum
nitrogen
zinc
chromium
iron
nickel
tin
lead
hydrogen*
copper
mercury
silver
platinum
gold

15. Practice Can Al replace Li? ____ Can Cu replace Au? ____
Can Br replace I? ____
Can Cl replace F? ____ NO
YES
YES NO

16. H2 + PbCl2  No rxn Practice Problems: H2 + PbCl2  Cl2 + KBr 
Zn CuS  +1 +2 -1
H2 + PbCl2 
No rxn

17. Any Diatomic atoms? K Cl Br Cl2 + KBr  BALANCE Cl2 + KBr  KCl + Br2
Practice Problems:
H2 + PbCl2 
Cl KBr 
Zn CuS 
Any Diatomic atoms? +1 -1 -1 +1 -1 K Cl + Br
Cl2 + KBr  2
BALANCE
Cl2 + KBr  KCl + Br2 2 2

18. Any Diatomic atoms? Zn S Cu Zn + CuS  BALANCE Zn + CuS  ZnS + Cu
Practice Problems:
H2 + PbCl2 
Cl KBr 
Zn CuS 
Any Diatomic atoms? -2 +2 +2 +2 -2 Zn S + Cu
Zn + CuS 
BALANCE
Zn + CuS  ZnS + Cu

19. AB + CD  AD + CB Double Replacement
Ions from 2 ionic compounds switch places.
--put the inside ions together and the outside ions together
--positive ion always goes first in the compound!
Analogy: 2 couples are dancing, and they switch partners
AB + CD  AD + CB

20. Double Replacement Pb(NO3)2(aq)+ KI(aq)  PbI2(s)+ KNO3(aq) Example:
FeCl2 + Na2CO3  2 NaCl + FeCO3
Pb(NO3)2(aq)+ KI(aq) 
PbI2(s)+ KNO3(aq)

21. Practice #1 BALANCE Na2CO3 + Ca(NO3)2 
Na2CO3 + Ca(NO3)2  NaNO3 +CaCO3 +2 -1 +1 -2
NaNO3 +
CaCO3 2
BALANCE

22. Practice #2 BALANCE K3PO4 + MgCl2  K3PO4 + MgCl2  KCl + Mg3(PO4)2+1 -3 +2 -1
KCl +
Mg3(PO4)2 2 3 6
BALANCE

23. CH4(g) + 2O2(g)  CO2(g) + 2H2O(g)
Combustion
Also known as burning; always follows the same form:
The compound always burns in oxygen gas and always releases carbon dioxide and water.
During incomplete combustion (a limited amt. of O2), carbon monoxide (CO) is also produced.
C & H (& sometimes O) + O2  CO2 + H2O
CH4(g) + 2O2(g)  CO2(g) + 2H2O(g)

24. Example:
2 C3H O2  6 CO H2O *always balance in order: C, H, O
Practice Problems:
CH O2 
C6H O2 
BALANCE 2
CO H2O 2
CO H2O 2 19 12 14