Alkenes and Crude Oil

Question 1

Why do we crack crude oil?

Answer 1

We crack crude oil to break down the long chain hydrocarbons in to lots of short chain hydrocarbons because the short chain hydrocarbons are in greater demand.

Question 2

How do you crack crude oil? What is the formula for this reaction?

Answer 2

Cracking is a thermal decomposition reaction. First of all you must heat the long chain hydrocarbon to vaporise it. The vapour must then be passed over a catalyst (aluminium oxide) at a very high temperature.

Question 3

Give the properties of alkenes. (the rap)

Answer 3

Alkenes, you are unsaturated. You’re just so overrated, you’ve got that double bond thing thing going on. Makes bromine water’s colour gone, gone, gone. They are unsaturated molecules. They have one double C=C bond. You can test for alkenes by seeing if they make bromine water turn colourless.

Question 4

What is the general formula for alkenes?

Answer 4

C_nH_2n

Question 5

What do you need to react Ethene with to produce ethanol? What is the problems with this way of making ethanol?

Answer 5

Ethene (C₂H₄) can be hydrated with steam (H₂O) in the presence of a catalyst to make ethanol.

At the minute this is cheap because there is lots of ethene but because Crude oil is a finite resource, it could become very expensive.

Question 6

Describe how to make ethanol using renewable resources. Include the word equation and any advantages to this way of making ethanol.

Answer 6

Word equation for fermentation.

sugar —> carbon dioxide + ethanol

Sugar is converted in to ethanol using yeast. Some advantages include that it can be done at much lower temperatures and doesn’t need complex equipment and that sugar is a renewable resource.

Question 7

How can alkenes can be used to make polymers?

Answer 7

Polymerisation!! This means joining lots of small alkene molecules (monomers) to make very large molecules (polymers).

Question 8

Describe three types of polymers and their uses.

Answer 8

• Elastic, stretchy polymers are used to create the stretchy LYCRA fibre for tights.
• Polymer hydro gel wound dressings keep wounds moist.
• Memory foam is an example of a smart material. It is a polymer that gets softer as it gets warmer.