Alkanes

Question 1

What it the trend in boiling point for straight chains?

Answer 1

• As chain length increases boiling point increases
• Surface area increases so London Forces are stronger
• Requires more energy to overcome

Question 2

What is the trend in boiling points for branched chains?

Answer 2

• The more branched chains the lower boiling point
• Chains cannot pack as closely together so there are fewer point go contact
• London forces are weaker so less energy is required to overcome

Question 3

How reactive are alkanes?

Answer 3

• Non polar due the C-H bonds
• Immiscible in water - don’t mix with water
• Unreactive - require very high activation energy to react

Question 4

What is the combustion reaction formula for alkanes?

Answer 4

• All hydrocarbons combust to form carbon dioxide and water
• Exothermic so one of the main uses of hydrocarbons is fuels
• Complete combustion - hot blue flame in pure oxygen
• Incomplete combustion - yellow and
  sootier flame.