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Types of Chemical Reactions. let’s classify. Why Classify Chemical Reactions?. “I wonder what will happen if I light a match in a room full of gasoline vapour ?” What type of reaction do you think will occur? Combustion—exothermic and rapid! How do you know this?.
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Types of Chemical Reactions let’s classify . . .
Why Classify Chemical Reactions? “I wonder what will happen if I light a match in a room full of gasoline vapour?” What type of reaction do you think will occur? Combustion—exothermic and rapid! How do you know this?
Five Types of Chemical Reactions • Synthesis • Decomposition 3. Combustion 4. Single Displacement 5. Double Displacement let’s look more closely at each type . . .
Synthesis Reactions Occur when two or more elements or compounds combine to form a new substance. These reactions come in the general form of: A + B AB eg. 8 Fe + S8 8 FeS
Predict the products . . . Na(s) + Cl2(g) NaCl(s) Al(s) + Br2(l) AlBr3(s) Fe(s) + Cl2(g) FeCl3(s)
Mg(s) + O2(g) MgO(s) Sb(s) + Cl2(g) SbCl3(s)
P4(s) + O2(g) P4O10(s) P4O10(s) + HOH(l) H3PO4(aq) CaO + HOH(l) Ca(OH)2(aq)
Reactions of Oxides with Water a) Metal oxide + HOH basic solution eg. Na2O(s) + HOH(l) NaOH(aq) b) Non-metallic oxide + HOH acidic solution eg. SO3(g) + HOH(l) H2SO4(aq)
Write the product(s) of each of the following synthesis reactions Zn(s) + S8(s) ZnS(s) Zn(s) + O2(g) ZnO(s) S8(s) + O2(g) SO2(g)
Synthesis reactions and Acid Precipitation CO2(g) + H2O(l) H2CO3(aq) S8(s) + O2(g) (unbalanced) SO2(g) SO2(g) + O2 (unbalanced) SO3(g) SO3(g) + H2O(l) (unbalanced) H2SO4(aq)
Decomposition Reactions A compound decomposes—or breaks down into its elements or into other compounds. C A + B A decomp. reaction is the opposite of a synthesis reaction.
Types of Decomposition Rxns • binary cmpd its elements • metal nitrate metal nitrite + O2 • metal carbonate metal oxide + CO2 • metal hydroxide metal oxide + H2O
Examples NaCl(s) Na(s) + Cl2(g) KNO3(s) KNO2(s) + O2 Na2CO3 Na2O + CO2 NaOH Na2O + H2O
Examples of decomposition reactions 2 HOH(l) 2 H2(g) + O2(g) NH4NO3(s) N2O(g) + 2 HOH(g) H2O2(aq) (with MnO2(s) catalyst) HOH(l) + O2(g)
What’s a catalyst? A catalyst increases the rate of a chemical reaction . . . but is not used up in the reaction. A catalyst is present at the beginning and at the end of a chemical reaction. eg. catalytic converter in an automobile’s exhaust system
More examples of decomprxns(with video clips) KClO3(s) + heat KCl(s) + O2(g) http://www.youtube.com/watch?v=7Xu2YZzufTM (NH4)2Cr2O7(s) + heat Cr2O3(s) + N2(g) + HOH(g) http://www.youtube.com/watch?v=6mJbcMOa0GA
Are the products of a decomposition reaction stable or unstable compounds? What product(s) have you noticed so far? N2, HOH, KCl, etc These are all stable compounds.
Q: What is Beethoven doing in his grave? A: Decomposing
Combustion Reactions Used for cooking, heat, transportation and more. Complete combustion of a C & H (& O) containing fuel in the presence of sufficient O2 yields CO2 and HOH Incomplete combustion yields C(s) + CO(g) + CO2(g) + H2O(g)
examples of combustion of C&H(&O) - containing fuels CH3CH2OH(l) + O2(g) (sufficient O2) CO2(g) + HOH(g) C8H18(l) + O2(g) incomplete combustion C(s) + CO(g) + CO2(g) + HOH(g) (Incomplete combustion—not enough O2 present) Is it possible to balance this equation?
Here’s what happened when we put a balloon full of H2 and O2 on top of a sheet of Al foil in a microwave oven. rxn is: 2 H2(g) + O2(g) 2 H2O(g) + energy
Can also have combustion of elements other than carbon eg. Mg(s) + O2(g) MgO(s) H2(g) + O2(g) HOH(g) How else could we classify these reactions? synthesis
Check out this video http://www.stumbleupon.com/su/4nU70a/current.com/entertainment/comedy/90267537_chemical-party.htm