OB: Double Replacement Reactions (4/5)
It takes 2 aqueous solutions to begin a double
replacement reaction.
The cations switch anions with each other.
The reaction occurs if a precipitate forms in the products.
If no precipitate forms, just a mixture formed, no chemical reaction
happened.
In the abstract: AB + XY
(AQ)
(AQ)
AY + XB
(AQ)
(S)
Must start with 2 AQ solutions,
must end with 1 AQ solution + 1 SOLID PRECIPITATE
How will you know if a product is soluble in water
(dissolves), or insoluble (a precipitate)? Use…
Take it out now…
Example reaction:
Copper (II) nitrate solution + ammonium carbonate solutions combine…
First we must write the formulas correctly (watch ion charges)
Cu+2 and NO3-1
then
NH4+1 and CO3-2
Cations switch their Anions
Cu(NO3)2(AQ) +
(NH4)2CO3(AQ)
NH4NO3 + CuCO3
Next, we check to see if our products are
written properly according to ion charges
Ammonium and nitrate are in 1:1 ratio OK,
Cu+2 with CO3-2
also 1:1 OKAY
Now we balance, then check table F for aqueous or solid
Cu(NO3)2(AQ)+
(NH4)2CO3(AQ)
2NH4NO3
+ CuCO3
The quick John Dalton, simple whole number ratio check is 1:1:2:1, okay.
Let’s look at table F. What’s AQ, what’s S ?
Cu(NO3)2(AQ) + (NH4)2CO3(AQ)
2 aqueous solutions to start
2NH4NO3(AQ) + CuCO3(S)
1 aqueous solution + 1 solid precipitate = DR
Demo Diagram 4/5 Double Replacement Reactions
2 AQ solutions combine, if you get 1 (AQ) and 1 (S) precipitate to form
then a double replacement reaction occurred.
If 2 AQ solutions result in 2 different AQ solutions, nothing really happened.
Abstract:
FG(AQ) + XY(AQ)
FY + XG [one AQ and one S!]
Word equation:
Sodium hydroxide and copper (II) sulfate solutions combine…
Skeleton:
Balanced:
DIAGRAM for Double Replacement
CuSO4(AQ)
Blue solution
Na2SO4(AQ)
Clear solution
NaOH(AQ)
Clear solution
Blue precipitate
Cu(OH)2 (S)
Every solution on the left side is soluble (dissolves in water).
There are only a couple of exceptions.
Halides are fluoride, chloride, bromide, and iodide solutions.
Every solution on the right side is insoluble (solid precipitate in water)
There are more than a few exceptions, but most of those you would already
find on the right side (like group 1 ions, or ammonium, or nitrate, etc.)
Always watch for the exceptions, let’s play now.
Match the name to the formula, Table F
each compound to decide AQ or S.
•
•
•
•
•
•
•
•
•
•
Silver chloride
Magnesium perchlorate
Sodium hydroxide
Calcium nitrate
Strontium sulfate
Barium acetate
Aluminum chlorate
Lead (II) bromide
Lithium sulfide
Ammonium chromate
•
•
•
•
•
•
•
•
•
•
NaOH
SrSO4
LiS
(NH4)2CrO4
AgCl
MgClO4
PbBr2
Ba(C2H3O2)2
CaNO3
AlClO3
Are these solutions
soluble in water (AQ) or insoluble (S)?
•
•
•
•
•
•
•
•
•
•
Silver chloride
Magnesium perchlorate
Sodium hydroxide
Calcium nitrate
Strontium sulfate
Barium acetate
Aluminum chlorate
Lead (II) bromide
Lithium sulfide
Ammonium chromate
•
•
•
•
•
•
•
•
•
•
AgCl(S)
MgClO4(AQ)
NaOH(AQ)
CaNO3(AQ)
SrSO4(S)
Ba(C2H3O2)2(AQ)
AlClO3(AQ)
PbBr2(S)
LiS(AQ)
(NH4)2CrO4(AQ)
Finish the word problems, do the formulas, balance the equations,
complete the phase symbols for both products.
Sodium chloride + lead (II) acetate solutions combine…
Potassium phosphate + calcium chloride solutions combine…
Finish the word problems, do the formulas, balance the equations,
complete the phase symbols for both products.
Sodium chloride + lead (II) acetate solutions combine…
NaCl(AQ) + Pb(C2H3O2)2(AQ)
2NaC2H3O2(AQ) + PbCl2(S)
Potassium phosphate + calcium chloride solutions combine…
K3PO4(AQ) + 3CaCl2(AQ)
3KCl2(AQ) + Ca3(PO4)2(S)
Finish the equations, balance the equations, complete the phase
symbols for both products.
BaCl2(AQ) + RbOH(AQ)
NH4CrO4(AQ) + Ca(NO3)2(AQ)
Finish the equations, balance the equations, complete the phase
symbols for both products.
BaCl2(AQ) + 2RbOH(AQ)
NH4CrO4(AQ) + Ca(NO3)2(AQ)
2RbCl(AQ)
+
Ba(OH)2(S)
2NH4NO3(AQ)
+
CaCrO4(S)
HW #4 Combustion Hand in Today,
#3 DR, to be handed in on Tuesday.
We will have a practice quiz NOW.
Hurry.
Watch Reactions Class #6 for Review,
we will NOT do that slide show in class.