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

1. Synthesis2. Decomposition3. Combustion4. Single Displacement5. 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 solutioneg. 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 asynthesis 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 decomp rxns (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 allstable 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 HOHIncomplete combustion yieldsC(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 an example of just how combustible methane is:

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