1. Quiz 5.1
In a chemical equation, “(aq)” means “aqueous”. What does this mean?
Balance the following: __Al2O3  __Al + __O2
Write the correct formula for sodium nitrate
Write the correct formula for carbonic acid

2. Quiz 5.1
In a chemical equation, “(aq)” means “aqueous”. What does this mean?
Balance the following: __Al2O3  __Al + __O2
Write the correct formula for sodium sulfide
Write the correct formula for sulfuric acid

4. How do you write net ionic equations?
5.2 Types of Reactions
How do you write net ionic equations?

5. Review

6. When the identity of a substance changes, a chemical reaction has occurred
Atoms are being reorganized by breaking and creating bonds
Reactants  Products

7. 5 major chemical reaction types
Combustion
Synthesis Reaction
Decomposition reaction
Single replacement reaction
Double replacement reaction

8. Combustion
A hydrocarbon fuel combusts with oxygen gas, releasing carbon dioxide and water
CH4+ 2O2  CO2 + 2H2O
2C8H18+ 25O2  16CO2 + 18H2O

9. Synthesis reaction Elements/compounds combine to form a new compound
A + B  AB
3H2(g) + N2(g)  2NH3(g)

10. Decomposition reaction
A compound breaks down into simpler elements/compounds
Opposite of synthesis reaction
AB  A + B
2H2O2 (l)  2H2O(l) + O2 (g)
***It does not breakdown into ions! NaCl breaking down into Na+ and Cl- is NOT a decomposition reaction

11. Single Replacement Reaction
An element in a compound is replaced to form a different compound
A + XY  X + AY
Zn(s) + 2HCl (aq)  ZnCl2(aq) + H2(g)
Zinc replaces hydrogen to form zinc chloride

12. Zn(s)+FeSO4(aq)→Fe(s)+ZnSO4(aq)
Zinc replaces iron to form zinc sulfate

13. Zn(s) + 2HCl (aq)  ZnCl2(aq) + H2(g)
Activity Series
Single replacement reaction will only occur if the lone metal is more active than the metal in the compound
Zn(s) + 2HCl (aq)  ZnCl2(aq) + H2(g)
The zinc is higher on the list than hydrogen, making it more active; reaction will take place

14. Fe(s)+ZnSO4(aq) → Zn(s)+FeSO4(aq)
Identify iron and zinc on the activity series
Since zinc is more active, iron cannot take away the sulfate (SO42-) away from zinc
Reaction does NOT occur

15. Practice
KCl + Na 
No reaction!
Mg + FeS 
Fe + MgS

16. Double Replacement Reaction
Two compounds exchange elements
AB + XY  AY + XB
Results in a precipitate (an insoluble compound, a compound that does not dissolve, a solid).
2KI(aq)+Pb(NO3)2(aq)→2KNO3(aq)+PbI2(s)
NaCl(aq) + AgNO3(aq)  NaNO3(aq) + AgCl(s)

17. What happens when things dissolve?
As salt dissolves, the salt breaks up into smaller ions.
Dissociation is the break up of these ions
The water surrounds individual ions due to the charges
Since the ions are split up individually, it seems to have “disappeared”
Does it really disappear?

18. NaCl(aq) means that NaCl has been dissolved, and is separated into individual ions, Na+ and Cl-

19. So how can we figure out the precipitate in a double replacement reaction?
NaCl(aq) + AgNO3(aq)  NaNO3(aq) + AgCl(s)
How do you know AgCl is solid, and not NaNO3?
Ans: Solubility Table!

20. Solubility Table: on Website
If compound is insoluble, the compound must be written with (s)
If compound is soluble, the compound must be written with (aq)
Hint: Soluble means able to be dissolved

21. Practice: Soluble?
AlBr3
Yes
PbSO4 No
KSO4
FePO4

22. Writing Ionic Equations
Separate (aq) substances into their cations and anions
CaCl2(aq) =
Ca2+(aq) + 2Cl-(aq)

23. Mg(NO3)2(aq)=
Mg2+(aq) + 2NO3-(aq)
ZnSO4(aq) =
Zn2+(aq) + SO42-(aq)

24. Do not separate (s), (l), or (g)
Ex. AgCl(s) is still just AgCl(s) because it is insoluble in water

25. So rewrite the following equation as an ionic equation
NaCl(aq) + AgNO3(aq)  NaNO3(aq) + AgCl(s)
Na+(aq) + Cl-(aq) + Ag+(aq) + NO3-(aq) 
Na+(aq) + NO3-(aq) + AgCl(s)

26. Notice that Na+ and NO3- are the same in the reactant and product sides
Nothing is happening to these ions, and are called spectator ions
When spectator ions are removed from the ionic equation, the remaining ions make the net ionic equation

27. Na+(aq) + Cl-(aq) + Ag+(aq) + NO3-(aq) 
Na+(aq) + NO3-(aq) + AgCl(s)
Spectator ions are cancelled out!
You are left with the net ionic equation:
Cl-(aq) + Ag+(aq)  AgCl(s)

28. Practice Write out the ionic and net ionic equation of the following:
2KI(aq)+Pb(NO3)2(aq)→2KNO3(aq)+PbI2(s)
2K+(aq) + 2I-(aq) + Pb2+(aq) + 2NO3-(aq) 
2K+(aq) + 2NO3-(aq) + PbI2(s)
Pb2+(aq) + 2I-(aq)  PbI2(s)

29. Categorize the following chemical reactions as single replacement, double replacement, combustion, combination, or decomposition.
Magnesium carbonate is heated strongly to produce magnesium oxide and carbon dioxide gas.
Solid potassium chlorate is heated to produce potassium chloride and oxygen gas.