Dr James Chemistry SPM Form 5 Chapter 2 Carbon Compounds

1. General Formula :
n=1,2,3…
Naming of alkanes:
Number
of Carbon
1 2 3 4 5 6 7 8
Molecular
formula
CH4 C2H6 C3H8 C4H10 C5H12 C6H14 C7H16 C8H18
Name Methane Ethane Propane Butane Pentane Hexane Heptane Octane
CnH2n+2
Alkanes

2. Structural formula shows how the
atoms in a molecule are bonded
together and by what types of bonds.
Example :
Ethane
C2H6
molecular formula structural formula

3. Physical
Properties
of Alkanes
Solubility
- dissolve in
organic solvents
- insoluble in
water
Physical state at
room temperature
- C1 to C4 are gases
- C5 to C17 are liquid
- C18> are solid
Melting and boiling
point
- low melting and
boiling point
Density
- less dense
than water
Electrical
conductivity
- cannot conduct
electricity
- because there
are no free
moving ions

4. Explain the effect of the increase in number of
carbon atoms in alkane molecules
 Size of molecule increase
 Melting point & boiling point increase
• The higher the number of carbon atoms, the higher
the melting & boiling point
• As the number of carbon atoms increases, the
molecule become bigger
• The force of attraction between the molecules
become stronger
• More heat energy is needed to overcome the force
of attraction between molecules

5. Boiling Point of Alkane

6. a. Combustion
1. Complete combustion:
produce CO2 + H2O
2. Incomplete combustion :
produce CO/C gas + H2O
C2H6 + O2 → CO2 + H2O
2CH4 + 3O2 → 2CO + 4H2O
CH4 + O2 → C + 2H2O
Chemical Properties of Alkanes

7. b. Halogenation
Reaction of alkanes with halogens.
takes place in sunlight (not occur in dark)
carbon-hydrogen bonds are broken and
new carbon-halogens bonds are formed
Substitution reaction: one atom or a group
of atoms in a molecule is replaced by
another atom or group of atoms
Example:
When a mixture of CH4 and chlorine is exposed to
ultraviolet light, 4 different products are formed
CH4 (g) + Cl2(g) → CH3Cl (g) + HCl(l)
Chloromethane hydrogen chloride

8. a. Formation of dichloromethane
b. Formation of trichloromethane
c. Formation of tetrachloromethane

9. • CH4 + Cl2 → CH3Cl + HCl
• CH3Cl + Cl2 → CH2Cl2 + HCl
• CH2Cl2 + Cl2 → CHCl3 + HCl
• CHCl3 + Cl2 → CCl4