C7 - Organic Chemistry

Question 1

What is a hydrocarbon?

Answer 1

A substance that consists of only hydrogen and carbon atoms.

Question 2

What is the general formula for an alkane?

Answer 2

CnH2n+2

Question 3

Name the first four alkanes.

Answer 3

1) Methane.
2) Ethane.
3) Propane.
4) Butane.

Question 4

What are the properties of alkanes?

Answer 4

• Have the general formula CnH2n+2.
• Alkanes are a homologous series.
• They are saturated compounds.

Question 5

How does the length of a hydrocarbon affect its properties?

Answer 5

1) The shorter the carbon chain, the less viscous it is.
2) Shorter carbon chains are more volatile, so they have lower boiling points.
3) The shorter the carbon chain, the more flammable the hydrocarbon is.
4) Short chain hydrocarbons are used as bottled gases, which are stored under pressure as liquids in bottles.

Question 6

What happens in complete combustion of a hydrocarbon?

Answer 6

• It occurs when there’s plenty of oxygen.
• Lots of energy is released.
• Both carbon and hydrogen are oxidised.
• Hydrocarbons are used as fuels due to the amount of energy released when they combust completely.

Question 7

What is crude oil and how is it formed?

Answer 7

• A fossil fuel.
• It is formed from the remains of plants and animals (mainly plankton) that died millions of years ago and were buried in mud.
• Over millions of years, with high temperatures and pressure, the remains turn into crude oil.

Question 8

What is crude oil used for?

Answer 8

1) Provides fuel for most modern transport.
2) Used to make polymers, solvents, lubricants and detergents.
3) Can bond to form different groups.

Question 9

What is cracking and why is it done?

Answer 9

• Cracking is the process of splitting up long chain hydrocarbons.
• This is done because short chain hydrocarbons are flammable, so they make good fuels and are in high demand.