Hydrocarbons and combustion

Question 1

What are the properties of carbon monoxide?

Answer 1

Colourless, Toxic, Odourless

Question 2

What can be created when alkanes are burned without enough oxygen?

Answer 2

Carbon monoxide

Question 3

What does the combustion of hydrocarbons involve when there is a good air supply?

Answer 3

• The release of energy

- The oxidation of carbon and hydrogen to create carbon dioxide and water

Question 4

Why don’t heavy fractions of crude oil make good fuels?

Answer 4

• Have low volatility
• Don’t ignite easily
• Have high boiling points

Question 5

What is cracking?

Answer 5

Cracking is the process that breaks down long-chain hydrocarbons into shorter-chain molecules that are more useful . Cracking is an example of a thermal decomposition reaction.

Question 6

What are the two methods

of cracking?

Answer 6

• Steam cracking

- Catalytic cracking

Question 7

What does steam cracking involve?

Answer 7

• Vapourised heavy hydrocarbons are combined with steam in a high temperature environment.
• Alkanes and alkenes are produced by this reaction.

e.g decane –> octane + ethene

Question 8

What does catalytic cracking involve>

Answer 8

• Vapourised heavy hydrocarbons are passed over the top of a heated catalyst.
• Alkenes and alkanes are produced by this reaction.

e.g hexane –> butane + ethene

Question 9

What are hydrocarbons?

Answer 9

Organic compounds made of carbon and hydrogen.

Question 10

What are the uses of alkenes?

Answer 10

• Being combined to make polymers

- Starting materials for chemicals like ethanol

Question 11

What is fractional distillation?

Answer 11

The process of separating crude oil into groups of hydrocarbons with similar numbers of carbon atoms. We call these groups of hydrocarbons “fractions”.

Question 12

Different-sized hydrocarbons have different boiling points. Fractional distillation separates hydrocarbons using their different boiling points. What are the steps to the process of fractional distillation?

Answer 12

1. EVAPORATION
   - We evaporate the crude oil by heating it.
   - Crude oil vapour is put into a fractionating column at the bottom and rises upwards.
2. CONDENSATION
   - The temperature is highest at the bottom of the column. Long-chain hydrocarbons condense at the bottom and are collected as liquids.
   - Short-chain hydrocarbons have lower boiling points. They pass up the column and condense at lower temperatures nearer the top

3.COLLECTION
The fuels are collected. They are then processed to create end products:
- Fuels (e.g. petrol, diesel) are a common end product.
- The petrochemical industry can use some fractions as feedstock (material used in an industrial process) to make products such as solvents, detergents, lubricants etc.

Question 13

What is a homologous series?

Answer 13

A family of similar compounds