Unit 4 - Lesson 8: Cracking Flashcards
Different hydrocarbons have different uses. How do we separate out these hydrocarbons?
We separate out hydrocarbons from raw crude oil using fractional distillation in an oil refinery.
What does crude oil produce more of?
Long chain hydrocarbons.
Are hydrocarbons more or less combustible? Does this make them more or less profitable? Is there a high or low demand for shorter fractions?
Hydrocarbons are less combustible, meaning they are harder to burn. This makes them LESS profitable. There’s a much higher demand for shorter fractions to fuel cars, trains and buses.
What does cracking do to long hydrocarbons and why is this needed?
Cracking breaks up long hydrocarbons to overcome this supply and demand problem.
What is cracking? What is it most often done to?
Cracking is the thermal decomposition of hydrocarbons. Most often alkanes.
What are alkanes?
Alkanes are compounds hydrocarbon chains with only single bonds.
What are alkenes?
Alkenes are hydrocarbons with a double carbon bond (C=C)
What does cracking (the thermal decomposition of hydrocarbons) produce?
Shorter hydrocarbons and alkenes.
What can be produced when cracking a long hydrocarbon?
Ethene and alkane.
What can be produced when cracking alkane (a pure hydrocarbon chain)?
Alkene (hydrocarbon with C=C) and more alkane.
Are the products of cracking random?
The products can be quite random, with multiple possibilities arising from one type of long chain alkane. Even hydrogen can be produced.
Is cracking profitable or non-profitable? Why?
Profitable. It produces more alkanes for petrol and alkenes to produce plastic.
What is organic chemistry?
Organic chemistry is the study of substances containing carbon.
Give four examples of cracking products from the same reactant:
C13H28 (l)
C13H28 (l) –> C2H4 (g) + C3H6 (g) + C8H18 (l)
C13H28 (l) –> 2C2H4 (g) + C9H20 (l)
C13H28 (l) –> 2C2H4 (g) + C3H6 (g) + C6H14 (l)
C13H28 (l) –> 2C2H4 (g) + C3H6 (g) + C6H12 (l) + H2 (g)
There are two methods for cracking. What are they?
- The first method uses heat (600-700 Degrees Celsius) and a catalyst. The catalysts are silicon dioxide SiO2 (silica) or aluminium oxide, Al2O3 (alumina).
- The second method uses higher temperatures (850 Degrees Celsius) with no catalyst. This is called thermal cracking.
Explain one method of cracking involving using a catalyst. Include the temperature and names of the catalysts. What is this method called?
Draw and label a diagram for catalytic cracking in a laboratory.
This method uses heat of 600-700 Degrees Celsius and a catalyst.
The catalysts are silicon dioxide, SiO2 (silica) or aluminium oxide, Al2O3 (alumina).
We can demonstrate this in a laboratory by heating mineral wool soaked in oil with a catalyst, producing a gas.
This method is called catalytic cracking.
EXAMPLE:
1. Soak a mineral wool in oil.
2. Put the mineral wool soaked in oil in a test tube with aluminium oxide catalyst over a blue-flame Bunsen burner.
3. Connect the test tube to another test tube in a body of water, and watch a gaseous product form in this empty test tube.
https://i.pinimg.com/736x/97/67/67/97676788bc0188e489d62dcef6f78625.jpg
Explain another method of cracking that doesn’t use a catalyst. Include the temperature. What is this method called?
The second method uses higher temperatures (850 Degrees Celsius) with no catalyst. This is called thermal cracking.
