Transcript Combination RxNs - Centennial School District

How do chemists know what to mix
together to make the products they
want???
Substances react with one another in
similar ways depending on their chemical
makeup and driving forces of different
situations.
Combination (or Synthesis)
when two or more substances react to form
one product
A + Z  AZ
Types: Synthesis
Example C + O2
C + O O

O C O
C
C
O O
C
CC
O O
C C C C C C CC
C
General:
A + B  AB
Practice: determine how the following
substances combine to form a new more
complex compound and then BALANCE
Mg(s) + O2 (g)  ???
Na(s) + Cl2 (g)  ???
Zn (s) + S (s)  ???
Zn (s) + I2 (s)  ???
Decomposition RxNs
When a complex compound undergoes a reaction
and breaks apart to produce two or more other
(more simpler) substances
– (heat or light may be used to do this)
AZ  A + Z
Types: Decomposition
Example: NaCl
Cl Na

General:
Cl
+
Na
AB  A + B
Types: Decomposition
Example 2HgO
O Hg

O Hg
General:
Hg
+
O O
Hg
AB  A + B
Decomposition of
Metal Hydrogen Carbonate
Compounds
When a metal hydrogen carbonate, upon
heating, will breaks down to yield a metal
carbonate compound, water and carbon
dioxide
2NaHCO3 (s)  Na2CO3 (s) + H2O(g) + CO2 (g)
The delta (triangle) in the equation
means that heat is applied
Decomposition of Metal Carbonate
Compounds
When a metal carbonate, after prolonged
heating, breaks down to yield a metal
oxide compound and carbon dioxide
CaCO3 (s)  CaO (s) + CO2 (g)
Decomposition of Chlorate
Compounds
A chlorate will break down to yield its
binary salt and oxygen gas.
KClO3 (s)  KCl (s) + O2 (g)
Practice: determine how each complex
compound will break down into simpler
substances and then BALANCE
NO2  ???
CaCO3  ???
KHCO3  ???
H2O  ???
Combustion
• Rapid reaction that produces a flame
• Involves O2 from the air as a reactant
C3H8 (g) + O2 (g)  CO2 (g) + H2O (g)
– C3H8 is common propane from your gas grill
– This is the complete combustion of propane
• Hydrocarbons are compounds that contain
ONLY carbon and hydrogen
• Complete combustion of hydrocarbons in
oxygen produces ONLY water and carbon
dioxide
Practice: determine the products of
these complete combustion reactions
and then BALANCE
C6H12 + O2  ???
CH4 + O2  ???
C4H8 + O2  ???
Single Displacement RxNs
When one more reactive metal (as per the activity
series) displaces another less active metal (or
hydrogen) from a compound or solution
A(s) + BZ  AZ + B(s)
Types: Single displacement
Example: Zn + CuCl2
Cu
Cl
+
Cl
General:
Zn

Zn
Cl
+
Cu
Cl
AB + C  AC + B
Element Reactivity
Activity Series
More Active
Foiled again –
Aluminum loses to Copper
Halogen Reactivity
F2
Cl2
Br2
I2
Less Active
Li
K
Ba
Sr
Ca
Na
Mg
Al
Mn
Zn
Cr
Fe
Co
Ni
Sn
Pb
H2
Cu
Ag
Hg
Pt
Au
How to determine if a single replacement
reaction will occur…
when Mg (s) + CoSO4 (aq) ?
1) Find both metals (Mg & Co) on activity series
2) If lone metal (Mg) is higher up on activity series than the
metal in the compound (Co)…Mg is more reactive thus it
will take Co’s position and replace it in the compound
3) If Mg is not more reactive…then No Reaction occurs…
– HERE…Mg is higher up on the activity series so it is more
reactive than Co …THUS the reaction WILL occur
Mg(s) + CoSO4 (aq)  MgSO4 (aq) + Co(s)
Types of Reactions
Practice (determine if a reaction will occur, if a
reaction occurs then predict the products and
balance if necessary))
• Zn(s) + HBr (aq) 
• Mg(s) + H2O (l) 
• Cd(s) + HNO3 (aq) 
• Al (s) + H2SO4 (aq) 
3. Single Replacement Reactions
•
•
•
Single Replacement Reactions occur when
one element replaces another in a compound.
A metal can replace a metal (+) OR
a nonmetal can replace a nonmetal (-).
element + compound product + product
A + BC  AC + B (if A is a metal) OR
A + BC  BA + C (if A is a nonmetal)
(remember the cation always goes first!)
When H2O splits into ions, it splits into
H+ and OH- (not H+ and O-2 !!)
4. 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
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)  2 KNO3(aq) + BaSO4(s)
Practice
•
Predict the products. Balance the equation
5.
HCl(aq) + AgNO3(aq) 
CaCl2(aq) + Na3PO4(aq) 
Pb(NO3)2(aq) + BaCl2(aq) 
FeCl3(aq) + NaOH(aq) 
H2SO4(aq) + NaOH(aq) 
6.
KOH(aq) + CuSO4(aq) 
1.
2.
3.
4.
Will a compound dissolve in water?
• A compound that DOES dissolve in water its called soluble
• A compound that DOES NOT dissolve in water its called insoluble
1) Write the formula of the following compounds
2) Predict if each compound will dissolve in water
•
•
•
•
Sodium chloride
Barium acetate
Potassium sulfate
Calcium phosphate
3) Use your solubility guidelines to check to see if you “guessed” correctly
((find the anion on the left side of the table and determine if it IS or IS
NOT soluble…then check the exceptions to each on the right side of the
table))
Precipitation (exchange or metathesis)
When two soluble compounds exchange ions (replace
OR displace one another) in order to form at least one
insoluble product (this is insoluble and falls out of
solution as a precipitate)
AX + BZ  AZ + BX
• either AZ or BX MUST be a precipitate
if no precipitate forms then no reaction occurs
Will a precipitate form?
Use Your Solubility Guidelines:
1) Note the individual ions present
2) Consider how each ion could “switch partners” to
form new combinations
3) Use the guidelines to determine ((find the anion on the left
side of the table and determined if it is OR is not soluble…then check
the exceptions to each on the right side of the table))
if the new combinations of “switched partners” are
insoluble (do not dissolve in water)
4) The insoluble possibility will force the reaction to
occur by forming a precipitate and falling out of
solution
Will a precipitate form…
when solutions of Mg(NO3)2 and NaOH are
mixed?
• All are aqueous so you have ions Mg+2 & NO3- ; Na+ & OH• Possible interacts are Mg+2  OH- and Na+ NO3• Checking solubility guidelines…most hydroxides (OH’s) are
insoluble and Mg(OH)2 is NOT an exception the reaction
occurs as
Mg(NO3)2 (aq) + 2NaOH (aq)  Mg(OH)2 (s) + 2NaNO3 (aq)
Practice: determine if a reaction occurs; if
yes, then predict the products and balance
the equation
MgSO4(aq) + BaCl2(aq) ???
AlBr3(aq) + Na2Cl2(aq)  ???
AgC2H3O2 (aq) + SrI2(aq)  ???
FeSO4(aq) + Ca(OH) 2(aq)  ???
Ionic Equations
Shows ions completely dissolved in water (strong electrolytes) as
ions in the chemical equation
Mg(NO3)2 (aq) + 2NaOH (aq)  Mg(OH)2 (s) + 2NaNO3 (aq)
Equation showing chemical formulas only is called molecular equation
Mg+2(aq) + 2(NO3)-(aq) + 2Na+(aq) + 2 OH-(aq)  Mg(OH)2 (s) + 2Na+(aq) + 2NO3- (aq)
Equation showing ALL IONS PRESENT (as ions) is called complete ionic equation
Mg+2(aq) + 2 OH- (aq)  Mg(OH)2 (s)
Equation showing ONLY IONS THAT TAKE PART IN REACTION (as ions) is called
NET ionic equation
Ions that do not take part in reaction (appear in identical forms on both sides) are called
spectator ions
If every ion in a complete ionic equation is a spectator, then NO
reaction occurs!!!
Practice
Write the complete ionic reaction for
AgC2H3O2 (aq) + SrI2(aq)  ???
AND THEN Write the corresponding net
ionic reaction
Practice
Write the complete ionic reaction for
FeSO4(aq) + Ca(OH) 2(aq)  ???
AND THEN Write the corresponding net
ionic reaction