Chemical Reactions
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CHM 1010
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Barbara Gage
Chemical Reaction
• Chemical change = chemical reaction
Changes may be visible:
• color change
• cloudiness (precipitation)
• gas formed (bubbles and/or odor)
• reactant decreases (without dissolving)
• energy is released or absorbed
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Chemical Equations
• Chemical changes can be written
symbolically. The symbolic
representation is called a chemical
equation.
Carbon reacts with oxygen to form carbon
dioxide.
C + O2  CO2
reactants
products
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Chemical Equations
• Reaction arrows can go in either
direction:
2 H2 + O2

• Or both directions:
NH4OH  NH3
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2 H2O
+ H2O
Barbara Gage
Or…
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Chemical Equations
• Because of the Law of Conservation of
Matter, you must account for all atoms
in a chemical change.
Carbon reacts with oxygen to form carbon
monoxide.
C
+ O2 
CO
2C
+ O2  2 CO
Equation is now balanced.
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coefficient
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Chemical Equations
• A sample of propane, C3H8, when ignited
with oxygen produces carbon dioxide
and water.
C3H8
+
C3H8
+ 5 O2 
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O2 
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CO2 + H2O
3 CO2 + 4 H2O
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Chemical Reactions
Al +
O2  Al2O3
CaCO3 + HI 
CaI2 + CO2 + H2O
Na3PO4 + BaCl2  NaCl + Ba3(PO4)2
C4H10
+ O2  CO2
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+ H2O
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Chemical Equations
• If you have information on the states of
matter, that can be added to the equation.
s = solid l = liquid g = gas aq = aqueous
Aqueous silver nitrate reacts with aqueous
potassium chloride to form solid silver
chloride and aqueous potassium nitrate.
AgNO3 (aq) + KCl (aq)  AgCl (s) + KNO3 (aq)
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Barbara Gage
Balancing Tips…
• Balance polyatomic ions that stay intact
as a single unit.
• Leave hydrogens and oxygens to the last
(oxygen very last)
• Be sure to reduce the coefficients to
the smallest whole numbers.
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Before
• Write the balanced
chemical equation
for the change in
the boxes and
indicate the reaction
type.
After
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Let’s look at the lab rxns…
• Mg (s) + HCl (aq) ------->
• CuCO3 (s) ---------->
• Mg (s)
+
------------->
• NaHCO3 (s) + HCl (aq)----->
• CuSO4 (aq) + Fe (s) -------->
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Barbara Gage
Let’s look at the lab rxns…
• CoCl2 (aq) + Na3PO4 (aq) –>
• KClO3 (s) + --------->
• Fe (s)
+
---------->
• HCl (aq) + NaOH (aq) ---->
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• Mg (s) + 2 HCl (aq) -------> MgCl2 (aq) + H2 (g)
• CuCO3 (s) +
• 2Mg (s)
+
-------------> CuO (s) + CO2 (g)
O2 (g) -------------> 2MgO (s)
• NaHCO3 (s) + HCl (aq)---> NaCl (aq) + H2CO3 (aq) ---->
NaCl (aq) + H2O (l) + CO2 (g)
• CuSO4 (aq) + Fe (s) --------> Cu (s) + FeSO4 (aq)
• 3CoCl2(aq) + 2Na3PO4(aq) –>Co3(PO4)2(s) + 6NaCl (aq)
• 2KClO3 (s) +
• 2Fe (s)
-----------------> 2 KCl (s) + 3 O2 (g)
+ O2 (g) ---------------> 2 FeO (s)
• HCl (aq) + NaOH (aq) ----> NaCl (aq) + H2O (l)
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Barbara Gage
Types of Reactions
• 1) Combination or Synthesis
• elements or (element + compound) or
compounds ------> compound
•
Fe (s) +
S (s) ------> FeS (s)
•
O2 (g) + 2 CO (g) ------> 2 CO2 (g)
•
H2O (l) + SO3 (g) ------> H2SO4 (aq)
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• Mg (s) + 2 HCl (aq) -------> MgCl2 (aq) + H2 (g)
• CuCO3 (s) +
• 2Mg (s)
+
-------------> CuO (s) + CO2 (g)
O2 (g) -------------> 2MgO (s)
• NaHCO3 (s) + HCl (aq)---> NaCl (aq) + H2CO3 (aq) ---->
NaCl (aq) + H2O (l) + CO2 (g)
• CuSO4 (aq) + Fe (s) --------> Cu (s) + FeSO4 (aq)
• 3CoCl2(aq) + 2Na3PO4(aq) –>Co3(PO4)2(s) + 6NaCl (aq)
• 2KClO3 (s) +
• 2Fe (s)
-----------------> 2 KCl (s) + 3 O2 (g)
+ O2 (g) ---------------> 2 FeO (s)
• HCl (aq) + NaOH (aq) ----> NaCl (aq) + H2O (l)
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Types of Reactions
• 2) Decomposition or Analysis
• compound ------> elements or (element
and compound) or compounds
•
2 HgO (s) -----> 2Hg (l) + O2 (g)
•
2 KBrO3 (s) -----> 2 KBr (s) + 3 O2 (g)
•
CaCO3 (s) ------> CaO (s) + CO2 (g)
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Barbara Gage
• Mg (s) + 2 HCl (aq) -------> MgCl2 (aq) + H2 (g)
• CuCO3 (s) +
• 2Mg (s)
+
-------------> CuO (s) + CO2 (g)
O2 (g) -------------> 2MgO (s)
• NaHCO3 (s) + HCl (aq)---> NaCl (aq) + H2CO3 (aq) ---->
NaCl (aq) + H2O (l) + CO2 (g)
• CuSO4 (aq) + Fe (s) --------> Cu (s) + FeSO4 (aq)
• 3CoCl2(aq) + 2Na3PO4(aq) –>Co3(PO4)2(s) + 6NaCl (aq)
• 2KClO3 (s) +
• 2Fe (s)
-----------------> 2 KCl (s) + 3 O2 (g)
+ O2 (g) ---------------> 2 FeO (s)
• HCl (aq) + NaOH (aq) ----> NaCl (aq) + H2O (l)
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Barbara Gage
Types of Reactions
• 3) Single Replacement
element + compound -------->
element + compound
• Cu (s) + 2AgNO3 (aq) ---->2Ag (s) +
Cu(NO3)2 (aq)
•
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•Mg (s) + 2 HCl (aq) -------> MgCl2 (aq) + H2 (g)
•CuCO3 (s) +
•2Mg (s)
+
-------------> CuO (s) + CO2 (g)
O2 (g) -------------> 2MgO (s)
•NaHCO3 (s) + HCl (aq)---> NaCl (aq) + H2CO3 (aq) ---->
NaCl (aq) + H2O (l) + CO2 (g)
•CuSO4 (aq) + Fe (s) --------> Cu (s) + FeSO4 (aq)
•3CoCl2(aq) + 2Na3PO4(aq) –>Co3(PO4)2(s) + 6NaCl (aq)
•2KClO3 (s) +
•2Fe (s)
-----------------> 2 KCl (s) + 3 O2 (g)
+ O2 (g) ---------------> 2 FeO (s)
•HCl (aq) + NaOH (aq) ----> NaCl (aq) + H2O (l)
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Barbara Gage
Types of Reactions
• 4)
Double Replacement
compound + compound —> compound +compound
AgNO3 (aq) + NaCl (aq) —> AgCl (s) +NaNO3 (aq)
• Double Replacement Rxns:
Solid forming
AgNO3 (aq) + NaCl (aq) —> AgCl (s) +NaNO3 (aq)
Gas-forming
KHCO3 (aq) + HCl (aq) ----> KCl (aq) + CO2 (g) +H2O (l)
Acid-Base
HCl (aq) + KOH (aq) ----> KCl (aq) + H2O (l)
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•Mg (s) + 2 HCl (aq) -------> MgCl2 (aq) + H2 (g)
•CuCO3 (s) +
•2Mg (s)
+
-------------> CuO (s) + CO2 (g)
O2 (g) -------------> 2MgO (s)
•NaHCO3 (s) + HCl (aq)---> NaCl (aq) + H2CO3 (aq) ---->
NaCl (aq) + H2O (l) + CO2 (g)
•CuSO4 (aq) + Fe (s) --------> Cu (s) + FeSO4 (aq)
•3CoCl2(aq) + 2Na3PO4(aq) –>Co3(PO4)2(s) + 6NaCl (aq)
•2KClO3 (s) +
•2Fe (s)
-----------------> 2 KCl (s) + 3 O2 (g)
+ O2 (g) ---------------> 2 FeO (s)
•HCl (aq) + NaOH (aq) ----> NaCl (aq) + H2O (l)
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Barbara Gage
Types of Reactions
• 5) Oxidation-Reduction (redox)
CH4 (g) + 2O2 (g) ----> CO2 (g) + 2H2O (l)
2Mg (s) + O2 (g) -----------> 2MgO (s)
4HCl (aq) + 3FeCl2 (aq) + KMnO4(aq) -->
MnO2(s) + KCl(aq) + 3FeCl3(aq) + 2H2O(l)
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Mg (s) + 2 HCl (aq) -------> MgCl2 (aq) + H2 (g)
CuCO3 (s) +
2Mg (s)
+
-------------> CuO (s) + CO2 (g)
O2 (g) -------------> 2MgO (s)
NaHCO3 (s) + HCl (aq)---> NaCl (aq) + H2CO3 (aq) ---->
NaCl (aq) + H2O (l) + CO2 (g)
CuSO4 (aq) + Fe (s) --------> Cu (s) + FeSO4 (aq)
3CoCl2(aq) + 2Na3PO4(aq) –>Co3(PO4)2(s) + 6NaCl (aq)
2KClO3 (s) +
2Fe (s)
-----------------> 2 KCl (s) + 3 O2 (g)
+ O2 (g) ---------------> 2 FeO (s)
HCl (aq) + NaOH (aq) ----> NaCl (aq) + H2O (l)
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Solubility Rules
• Reactants and products of reactions
may be soluble.
• Use solubility rules to label them.
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Solubility Rules
Soluble Ionic Compounds
• All common compounds of Group IA (1) ions and ammonium ion are
soluble.
• All common nitrates, acetates, and most perchlorates are soluble.
• All common chlorides, bromides, and iodides are soluble, except for
those of silver (I), lead (II), copper (I) and mercury (I). All common
fluorides are soluble except those of lead (II) and Group IIA (2).
• All common sulfates are soluble except those of calcium, strontium,
barium, silver (I), and lead (II).
Insoluble Ionic Compounds
• All common metal hydroxides are insoluble, except those of Group IA
(1) and the larger members of Group IIA (2) (beginning with calcium).
• All carbonates and phosphates are insoluble, except those of Group IA
(1) and ammonium ion.
• Most other combinations not mentioned above (such as chromates,
oxides, sulfides) are insoluble, except those of Group IA (1) and
ammonium ion.
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Barbara Gage
Predicting Reactions…
• Complete and balance the following:
copper(II) chloride reacts with sodium
hydroxide
• CuCl2 (aq) + NaOH (aq) 
• Double displacement reaction…
CuCl2 (aq) + NaOH (aq)  Cu(OH)2 + NaCl
• CuCl2 (aq) + 2 NaOH (aq)  Cu(OH)2 (s)
+ 2 NaCl (aq)
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Barbara Gage
Ionic reactions
• Ionic compounds in solution dissociate into
ions.
• CuCl2 (aq) + 2 NaOH (aq)  Cu(OH)2 (s) +
2 NaCl (aq)
Is actually…
• Cu2+ (aq) + 2 Cl- (aq) + 2 Na+ (aq) + 2 OH(aq) Cu(OH)2 (s) + 2 Na+ (aq) + 2 Cl- (aq)
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Barbara Gage
Net Ionic Reactions
• Cu2+ (aq) + 2 Cl- (aq) + 2 Na+ (aq) + 2 OH- (aq)
 Cu(OH)2 (s) + 2 Na+ (aq) + 2 Cl- (aq)
• Cu2+ (aq) + 2 Cl- (aq) + 2 Na+ (aq) + 2 OH- (aq)
 Cu(OH)2 (s) + 2 Na+ (aq) + 2 Cl- (aq)
• Cu2+ (aq) + 2 OH- (aq)  Cu(OH)2 (s)
net ionic equation
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Barbara Gage
Net Ionic Reactions
•
•
•
•
Lead (II) nitrate reacts with potassium iodide
Pb(NO3)2 + KI 
Pb(NO3)2 + KI  PbI2 + KNO3
Pb(NO3)2 (aq) + 2 KI (aq) PbI2 (s) + 2 KNO3 (aq)
• Pb2+ (aq) + 2 NO3- (aq) + 2 K+ (aq) + 2 I-  PbI2 (s) +
2 K+ (aq) + 2 NO3- (aq)
• Pb2+ (aq) + 2 NO3- (aq) + 2 K+ (aq) + 2 I-  PbI2 (s) +
2 K+ (aq) + 2 NO3- (aq)
• Pb2+ (aq) + 2 I-(aq)  PbI2 (s)
net ionic equation
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Barbara Gage