1. Double Displacement Reactions + +

2. Types: Double displacement
Example: MgO + CaS S O  Mg Ca + O S Mg Ca +
General: AB + CD  AD + CB

3. Double Replacement Reactions
Double Replacement Reactions occur when a metal replaces a metal in a compound and a nonmetal replaces a nonmetal in a compound
Compound + compound  product + product
AB + CD  AD + CB

4. Double Replacement Reactions
Think about it like “foil”ing in algebra, first and last ions go together + inside ions go together
Example:
AgNO3(aq) + NaCl(s)  AgCl(s) + NaNO3(aq)
Another example:
K2SO4(aq) + Ba(NO3)2(aq)  KNO3(aq) + BaSO4(s)

5. For predicting products!

6. Double Displacement Rxns
2 soluble ionic compounds trade cations (+ve ions)
General Equation
AB + CD  CB +AD
3 possible products
Precipitate
Gas
Water

7. 4.3 Double Displacement Double Displacement Reactions Continued:
This time using the SOLUBILITY TABLE!
3 stipulations must be met for DD to occur or NO RXN.

8. Will a precipitate form?
Precipitate= an insoluble solid
If the product is insoluble in water , a precipitate will form (the compound is solid).
If the product is soluble in water, no precipitate forms (the compound is aqueous)
How do we know which compounds are soluble?
Use a solubility table

9. Rule
Exception
Nitrates (NO3-) are soluble
None
Halides (Cl- , Br- , I-) are soluble
Ag+, Hg2+, Pb2+
Sulfates (SO42-) are soluble
Ca2+, Ba2+, Pb2+, Hg2+, Ag+
Sulfides (S2-) are insoluble
NH4+ and ions of groups 1 and 2
Carbonates (CO32-)are insoluble
NH4+ and ions of group 1
Phosphates (PO43-)are insoluble
Hydroxides (OH-)are insoluble
Ca2+, Ba2+, Sr2+, and ions of group 1

10. Example #1
Aqueous solution of lead(II) nitrate is added an aqueous solution of potassium iodide. Predict the products, balance the chemical equation and predict the solubility of the products.
Dissociation = breaking into ions in water
Products
Pb2+ NO3-
K+ I-

11. Soluble – all nitrates are soluble
Example #1: Con’t
Skeleton Equation
Pb(NO3)2 + KI PbI2 + KNO3
Balanced Equation:
Pb(NO3)2 + 2KI PbI2 + 2KNO3
Add states to the equation:
Reactants are both aqueous
Go to the table
Lead (II) iodide
Potassium nitrate
Insoluble due to lead(II) ion (precipitate forms)
Soluble – all nitrates are soluble

12. Ex #2abc: Determine the products, balance and predict state of the products
Silver(I) nitrate (aq) + potassium sulfate (aq) 
Li2CO3 (aq) + NaCl (aq)
Mercury(II) nitrate(aq) + Lithium bromide(aq) 

13. Double Displacement Rxns Producing Gases
3 situations where gases are produced:
Carbonates react with acids
Sulfites react with acids
Ammonium salts react with bases
In all cases the product containing the carbonate, sulfite or ammonium ion breaks down into H2O and a gas.

14. Example #3: Carbonate + Acid
CaCO3(s) HCl(aq)  CaCl2(aq) H2CO3(aq)
CO2(g) + H2O(l)
The final equation is:
CaCO3(s) HCl(aq)  CaCl2(aq) + CO2(g) + H2O(l)
Decomposes

15. Example #4: Ammonium with Base
NH4Cl(aq) NaOH(aq)  NaCl(aq) NH4OH(aq)
NH3(g) + H2O(l)
The final equation is:
NH4Cl(aq) NaOH(aq)  NaCl(aq) + NH3(g) + H2O(l)
Decomposes

16. Example #5: Sulfite with Acid
Na2SO3(s) HCl(aq)  NaCl (aq) + H2SO3 (aq)
SO2 (g)+ H2O(l)
The final equation is:
Na2SO3(s) + HCl(aq)  NaCl (aq) + SO2(g) + H2O(l)
Decomposes

17. How do we know when a gas will form?
If one of the products is:
H2CO3 (ag)  CO2(g) + H2O(l)
H2SO3(aq)  SO2(g) + H2O(l)
NH4OH(aq)  NH3(g) + H2O(l)
= decomposes into
Remember, we still need to show the other product of the double displacement rxn.

18. Practice: Determine the products, states and balance the equation
Na2CO3 (aq) + HBr(aq) 

19. Ex #6: Neutralization Reactions
Double displacement rxn involving an acid and a base as reactants
Products are a salt and water
Eg. HNO3(aq) + KOH(aq)  KNO3(aq) + H2O(l)

20. For the following neutralization rxn: Predict the products, states and balance the equation
HCl(aq) + NaOH(aq)  H2SO4(aq) + CaOH(aq) 

21. Wrap-up of Double Displacement Rxns
Remember!!!
Double displacement rxns only happen when:
A precipitate is formed
A gas is formed
Water is formed
In all other cases, the ions stay in solution!!!
No rxn happens!!!

22. Animations for Double Displacement Rxns

23. Net Ionic Equations
Used when a precipitate is formed in a double displacement rxn.
Soluble ionic compounds are present in solution as aqueous ions.
disolves in water
NaCl(s)  Na+ + Cl-
K2SO4(s)  K+ + SO42-

24. Why use a Net Ionic Equation
It is the ions that will join to create the precipitate, by looking at the ions we get a better idea of what is happening in the solution.
Eg. For the reaction:
K2CO3 (aq) + BaCl2 (aq) 
What are the potential products? Are they soluble?

25. Total Ionic Equations K2CO3(aq) + BaCl2(aq)  2KCl(aq) + BaCO3(s)
KCl  soluble From a
BaCO3  insoluble table of solubility
We can write the equation using ions for all aqueous compounds
Becomes,
2K+ (aq) + CO32- (aq) + Ba2+ (aq) + 2Cl- (aq) 2K+ (aq) + 2Cl- (aq) + BaCO3(s)

26. From Total  Net Ionic Equations
Total ionic equation – contains all ions/compounds
2K+ (aq) + CO32- (aq) + Ba2+ (aq) + 2Cl- (aq) 2K+ (aq) + 2Cl- (aq) + BaCO3(s)
The potassium and chloride ions we unchanged by the rxn (in red)
Because they do not take part in the rxn, we call them spectator ions
If we show only the ions involved in the rxn, we get a net ionic equation

27. Net Ionic Equations
Total ionic equation – contains all ions/compounds
2K+ (aq) + CO32- (aq) + Ba2+ (aq) + 2Cl- (aq) 2K+ (aq) + 2Cl- (aq) + BaCO3(s)
Net ionic equation – contains only ions involved in the reaction and the solid they form.
For the above reaction the net ionic equation is:
CO32- (aq) + Ba2+ (aq)  BaCO3(s)

28. Down side to the Net Ionic Equation
Do not show what aqueous were mixed
Ex CO32- (aq) + Ba2+ (aq)  BaCO3(s)
We don’t know which barium compound and which carbonate compound were mixed.
We do know that any reaction involving the combination of barium ions and carbonate ions will produce a precipitate! Try one out.

29. Rules for Net Ionic Equations
Solutions of soluble salts
(KCl, NaNO3 etc.) All written as ions
Solutions of strong acids
(HCl, HNO3, H2SO4 and HClO4)
Solutions of strong bases
(NaOH, KOH, Ba(OH)2)
All covalent compounds left in molecular form, states are written beside them.
Including all gases, liquids (eg. H2O) and soluble covalent compounds (eg. ethanol)

30. Steps for Writing a Net Ionic Equation
Identify Type of Reaction and Possible Products
Look Up Solubility of Both Products
Indicate States of Reactants and Products
Write Chemical Equation for Reaction
Balance Equation
Write Total Ionic Equation
Write Net Ionic Equation

31. Ex. Write the total ionic equation and net ionic equation for the reaction of barium sulfide with sodium sulfate.

32. Practice Predict the products. HCl(aq) + AgNO3(aq) 
CaCl2(aq) + Na3PO4(aq) 
Pb(NO3)2(aq) + BaCl2(aq) 
FeCl3(aq) + NaOH(aq) 
H2SO4(aq) + NaOH(aq) 
KOH(aq) + CuSO4(aq) 
AgCl(aq) + HNO3(aq)
Ca3PO4 (aq) + NaCl(aq)
PbCl2(aq) + Ba(NO3)2(aq)
Fe(OH)3(aq) + NaCl(aq)
H2O(aq) + Na2SO4(aq)
K2SO4 (aq) + Cu(OH)2(aq)