II. Five basic types of chemical reactions:
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Transcript of II. Five basic types of chemical reactions:
II. Five basic types of chemical reactions:
A. Synthesis (composition)
B. Decomposition
C. Single Replacement
D. Ionic or Double Replacement
E. Combustion
A. Synthesis (composition):
two or more elements or compounds may combine to form a more complex compound.
Basic form: A + X AX
Examples of synthesis reactions
Metal + oxygen metal oxide
ex. 2Mg + O2 2MgO
Nonmetal + oxygen nonmetallic oxide
ex. C + O2 CO2
Metal oxide + water metallic hydroxide
ex. MgO + H2O Mg(OH)2
Nonmetallic oxide + water acid
ex. CO2 + H2O H2CO3
Metal + nonmetal salt
ex. 2 Na + Cl2 2NaCl
A few nonmetals combine with each other. ex. 2P + 3Cl2 2PCl3
What do all of these have in common?
2Mg + O2 2MgO
C + O2 CO2
CO2 + H2O H2CO3
MgO + H2O Mg(OH)2
2 Na + Cl2 2NaCl
2P + 3Cl2 2PCl3Only one product is formed.
Example(from Chemistry Interactive 2.0 CD, disk 1)
Zinc + Iodine zinc iodide
Oxygen + Hydrogen Water
Practice Predicting Products of Synthesis Reactions
B. Decomposition:
A single compound breaks down into its component parts or simpler compounds.
Basic form: AX A + X
Examples of decomposition reactions:
Metallic carbonates, when heated, form metallic oxides and CO2 .
ex. CaCO3 CaO + CO2
Most metallic hydroxides, when heated, decompose into metallic oxides and water.
ex. Ca(OH)2 CaO + H2O
Metallic chlorates, when heated, decompose into metallic chlorides and oxygen.
ex. 2KClO3 2KCl + 3O2
Some acids, when heated, decompose into nonmetallic oxides and water.
ex. H2SO4 H2O + SO3
Some oxides, when heated, decompose.
ex. 2HgO 2Hg + O2
Some decomposition reactions are produced by electricity.
ex. 2H2O 2H2 + O2
ex. 2NaCl 2Na + Cl2
What do all of these have in common?
CaCO3 CaO + CO2
Ca(OH)2 CaO + H2O
2KClO3 2KCl + 3O2
H2SO4 H2O + SO3
2HgO 2Hg + O2
2H2O 2H2 + O2
They have only one reactant.
Example
Decomposition of ammonium dichromate
Practice Predicting Products of Decomposition Reactions
C. Single Replacement:
a more active element takes the place of another element in a compound and sets the less active one free.
Basic form: A + BX AX + B
or
AX + Y AY + X
Examples of replacement reactions:
Replacement of a metal in a compound by a more active metal.
ex. Fe + CuSO4 FeSO4 + Cu
Replacement of hydrogen in water by an active metal.
ex. 2Na + 2H2O 2NaOH + H2
ex. Mg + H2O MgO + H2
Replacement of hydrogen in acids by active metals.
ex. Zn + 2HCl ZnCl2 + H2
Replacement of nonmetals by more active nonmetals.
ex. Cl2 + 2NaBr 2NaCl + Br2
Examples(use Disk 2)
Practice Predicting Products of Replacement Reactions
D. Ionic or Double Replacement:
occurs between ions in aqueous solution.
A reaction will occur when a pair of ions come together to produce at least one of the following:
a precipitate a gas water or some other non-ionized substance.
Basic form: AX + BY AY + BX
Examples of ionic reactions:
Formation of precipitate.
ex. NaCl + AgNO3 NaNO3 + AgCl
ex. BaCl2 + Na2 SO4 2NaCl + BaSO4
Formation of a gas.
ex. HCl + FeS - FeCl2 + H2S
Formation of water. (If the reaction is between an acid and a base it is called a neutralization reaction.)
ex. HCl + NaOH NaCl + H2O
Formation of a product which decomposes.
ex. CaCO3 + HCl
CaCl2 + CO2 + H2O
Ammonium chloride + barium hydroxide
Example
Practice Predicting Products of Ionic Reactions
Combustion of Hydrocarbons:
When a hydrocarbon is burned with sufficient oxygen supply, the products are always carbon dioxide and water vapor.
If the hydrocarbon has an even number of carbons, start with a coefficient of 2 CxHy
Balance in this order: C, H, O
If the supply of oxygen is low or restricted, then carbon monoxide will be produced.
This is why it is so dangerous to have an automobile engine running inside a closed garage or to use a charcoal grill indoors.
NOTE:
The phrase "To burn" means to add oxygen unless told otherwise.
(CxHy) + O2 CO2 + H2O
ex. CH4 + 2O2 CO2 + 2H2O
ex. 2C4H10 13O2 8CO2 + 10H2O
Analyzing Chemical ReactionsOne Reactant?
yes
DecompositionNext slide
no
2 Ionic Compounds or Acid and Ionic Compound?
yes no
Double Replacement
Precipitate
Next slide
Neutralization Gas
Element and Compound?
yes no
Single Replacement
Metal
Hydrocarbon and O2
yesno
Combustion
Synthesis
no
Halogen Metallic oxide
One Reactant?yes
Decomposition
2 Ionic Compounds or Acid and Ionic Compound?yes
Double Replacement
Precipitate Gas Neutralization
no
Element and Compound?
yes no
Single Replacement
Hydrocarbon and O2?
Combustion
yesnono
Synthesis
no
Metal Halogen Metallic oxide
yes