Classifying Chemical Reactions

Is useful in predicting products

FIVE BASIC WAYS TO CLASSIFY CHEMICAL REACTIONS:

1. Synthesis2. Decomposition3. Single-Replacement4. Double-Replacement5. Combustion

Synthesis Reactions:Generic Reaction

X + Y-->XY Definition-Two

reactants combine to make one compound.

Note: X and Y can be compounds or elements.

2 Reactants and 1 Product

Analogy- Like a marriage

Predicting products using synthesis reactions1. Li + S→

2. Na + Cl₂→

3. Br₂ + K →

Decomposition Reactions:The generic formula of

a decomposition reaction is:

XY --> X + Y

In a decomposition reaction, a

compound is broken down into two (or

more) simpler substances.

1 Reactant and

2+ Products

Analogy-Like divorce

Predicting products using Decomposition ReactionsUse of Reference Tables (don’t guess)

ZnS

CaCO₃

Mg(OH)₂

H₂SO₄

Single Replacement ReactionsDiscovery Education Video

Single Replacement Reactions:

A + XY --> AY + X

In this type of reaction, one ( more active) element replaces a similar element in a compound.

Metal replaces metalNon-metal replaces

non-metal

1 free element + compound compound + 1 free element

Aggressive metal wins

Like finding a new girl or boy friend

Li Rb K Ca Na Mg Al Mn Zn Fe Ni Sn Pb

Cu Ag Pt

Au

Activity Series of Metals

Most active metal wins out

Activity Series of HalogensF₂ Most active halogen winsCl₂Br₂I₂

Examples of Single Replacement Reactions:

2Al + 3Fe(NO3)2 3Fe + 2Al(NO3)3

Zn + CuCl2

Mg + Pb(NO3)2

Fe + Na3PO4

K + ZnCl2

Double-Replacement Reactions:AB + XY --> AY +

XB

In a double-replacement

reaction, the two compounds

exchange places in a solution to form two

new compounds.

Note: Always ionic compounds or acids as the reactants

2 compounds 2 compounds

Like switching partners in square dancing

Predicting products based onDouble Replacement Reactions Na₂(CO₃)+ CuCl₂→

BaCl₂+ Na₂SO₄→

(NH₄)₂S+ Zn(C₂H₃O₂)₂→

Ca(OH)₂+ HCl→

Combustion reaction Fuel reacts with oxygen

to produce heat + carbon dioxide and water.

CH₄ + O₂(g) → CO₂ (g) + H₂O(g) + heat

Exothermic reaction

Combustion Reactions:

When a substance combines with

oxygen releasing a large amount of

energy in the form of light and heat, it is a combustion reaction.

Note: Hydrocarbon fuel is composed of C, H & sometimes O

Oxygen is needed to Burn things.

Fuel* + oxygen → carbon dioxide + water

Predicting products based on Combustion ReactionsHexane C₆H₁₄

Methanol CH₃OH

Glycerol C₃H₈O₃

FIVE BASIC WAYS TO CLASSIFY CHEMICAL REACTIONS:1. Synthesis 2 reactants1 product

(like marriage)

2. Decomposition 1 reactant 2 products(like divorce)

3. Single-Replacement(most aggressive element wins)

4. Double-Replacement (switch partners)

5. Combustion=Burning (need oxygen to burn things)

Practice Reactions

Use the Chemistry Reference Tables