Chemistry Topic 7//Hydrocarbons//Fractional Distillation/Cracking of Crude Oil

Question 1

What is a HydroCarbon

Answer 1

any compound that is formed from Hydrogen and carbon only

Question 2

What are 3 facts about Alkanes

Answer 2

1. Saturated
2. Homologous series
3. C-C single bonds

Question 3

What is an Alkane

Answer 3

A type of HydroCarbon which has C-C single bonds

Question 4

Why are alkanes Homologous series

Answer 4

Because Alkanes are a group of organic compounds that have similar reactivities

Question 5

Why are Alkanes Saturated

Answer 5

Because each carbon atoms forms four single covalent bonds

Question 6

What is the formula of Alkanes

Answer 6

CnH2n+2

Question 7

What is the first four alkanes and their formula

Answer 7

Methane - CH4
Ethane - C2H6
Propane - C3H8
Butane - C4H10

Question 8

The shorter the carbon chain of HydroCarbons ….

Answer 8

1. The more runny the hydrocarbon is
2. The more flammable it is
3. The more volatile it is (turns into gas at lower temp)
4. lower boiling point

Question 9

why is shorter chain hydrocarbon in more demand

Answer 9

they burn more efficiently (very flammable) and make better fuels than long hydrocarbons

Question 10

Describe what happens when complete combustion occurs with hydrocarbon

Answer 10

complete combustion with hydrocarbon with oxygen releases lots of energy but produces waste product like carbon dioxide and water

Question 11

What oxidises in this complete combustion of hydrocarbon and oxygen

Answer 11

carbon and hydrogen are oxidised and gains oxygen

Question 12

Why are hydrocarbons used as goof fuels

Answer 12

Due to the amount of energy released when they combust completely

Question 13

What is crude oil

Answer 13

made up of different hydrocarbons made over long period of time from remains of plants and animals mainly plankton that can be used as fuels

Question 14

How is crude oil separated by fractional distillation

Answer 14

1. The oil is heated until majority is turned into gas
2. Gases enter fractionating column where there is a temperature gradient (hot at bottom and cooler at top)
3. The longer hydrocarbons have high boiling points and condense back into liquids and drain out
4. the shorter hydrocarbons have low boiling points and condense and drain out much later on near top where it is cooler

Question 15

Explain why different fractions exit the column at different points

Answer 15

Inside fractionating column is a temperature gradient with hottest part at bottom and coolest at top. when hydrocarbons in the crude oil gas reach a part of the column where the temperature is lower than their boiling point, they will condense and drain out of column

Question 16

What are the 2 main uses of crude oil

Answer 16

1. Oil provides fuel for transport vehicles
2. Making of new compounds for use in things like polymers, solvents, detergents and lubricants

Question 17

What is Cracking

Answer 17

Thermal decomposition reaction which consists of splitting up long chain hydrocarbons

Question 18

Why is cracking useful

Answer 18

Long chain hydrocarbons are useless as they form thick gloopy liquids like tar and instead, short chain hydrocarbons are flammable so make good fuels and in high demand so is useful

Question 19

What does Cracking produce

Answer 19

Alkane and Alkenes

Question 20

What are the 2 methods of Cracking

Answer 20

Catalytic cracking
Steam cracking

Question 21

Describe Catalytic cracking

Answer 21

1. Apply heat to long chain hydrocarbon to vaporise them
2. The vapor can be passed over a hot powdered aluminium oxide catalyst
3. The long chain hydrocarbon splits apart into shorter chain of hydrocarbon made of an alkane and alkene

Question 22

Describe what happens in steam cracking

Answer 22

1. Heat a long chain of hydrocarbon to vaporise them
2. Then mix them with steam and then heat them to a very high temperature
3. The long chain hydrocarbon splits apart into shorter chain of hydrocarbon made of an alkane and alkene