Alkanes + Name of compounds + Homologous series

Question 1

Substituent Group --> name
F, Cl, Br, I
CnH2n+1, CH3
OH
NO2
NH2
C6H5
CN

Answer 1

Fluoro, Chloro, Bromo, Iodo
Alkyl, Methyl
Hydroxy
Nitro
Amino
Phenyl
Cyano

Question 2

Define structural Isomerism

Answer 2

occurs when two or more compounds have the same molecular formula but different structural formula

Question 3

Name the types of fuel

Answer 3

Coal
Natural gas (main constituent is methane)
Petroleum (a mixture of hydrocarbons that can be separated into factions)

Question 4

Name the fractions of the fractional distillation of Petroleum and their uses

Answer 4

Butane (refinery gas): bottled gas for heating and cooking
Petrol: fuel in cars
Kerosene: jet fuel
Diesel: fuel in diesel engines (lorries)
Fuel oil: fuel in ships and home heating services
Bitumen: making roads

Question 5

Define homologous series

Answer 5

A series of compounds in which all members have the same functional group with a same general formula and therefore have the same chemical properties, however different in physical properties (cuz the no. of C atoms in a chain gradually changes)
Each member of the series differs from the next by CH2 unit in all cases.

Question 6

Alkanes general formula

Answer 6

CnH2n+2

Question 7

Why are alkanes generally unreactive

Answer 7

This is because they do not have a functional group, which are responsible for the reactions of a compound.

Question 8

Physical properties of alkanes

Answer 8

• C1-C4: gases
  C5-C18: liquids
  >C18: solids
  This is because down the group the molecule size increases resulting in
  stronger force of attraction between molecules
• mp and bp increase down the group. Since there is stronger FOA between
  molecules, more energy is needed to break/overcome the forces.
• colourless and less dense than water. Density gradually increases
  as molecular size increases
• insoluble in water but soluble in organic solvents (e.g. ether
  and benzene)
• non conductors of electricity (cuz covalent compounds, no free ions)

Question 9

Chemical reactions of alkanes

Answer 9

1. Combustion 
   Complete -> CO2 + H2O
   Incomplete -> CO + H2O + C
2. Free radical substitution
    react with halogen in the presence of UV light. H substituted by halogen/

Question 9

Chemical reactions of alkanes

Answer 9

1. Combustion
   Complete -> CO2 + H2O
   Incomplete -> CO + H2O + C
2. Free radical substitution
   react with halogen in the presence of UV light. H substituted by halogen.
   produce salt + hydrogen chloride HCl
3. Catalytic Cracking
   Breakdown of alkanes into smaller hydrocarbons such as alkanes and
   alkenes and maybe Hydrogen by heat
   conditions: catalyst Al2O3/SiO2 ; 400 - 600 C