C9 - Crude Oil and Fuels

Question 1

What is crude oil

Answer 1

crude oil is a mixture of many different carbon compounds. Nearly all of the compounds are hydrocarbons

Question 2

What is a hydrocarbon

Answer 2

compounds which only contain hydrogen and carbon atoms

Question 3

What is the problem with crude oil from the ground

Answer 3

It has to many substances with different boiling points so before it can be used it must be separated into different substances with similar boiling points known as fractions

Question 4

what does distillation do

Answer 4

distillation separates liquids with different boiling points

Question 5

What is an alkane

Answer 5

saturated hydrocarbons. all the carbon-carbon bonds are single covalent bonds so this means that they contain as many hydrogen atoms as possible in each molecule

Question 6

what is the general formula for alkanes

Answer 6

CnH(2n+2)

Question 7

what are the first 4 alkanes

Answer 7

Methane (CH4), Ethane (C2H6), Propane (C3H8) and Butane (C4H10)

Question 8

Properties of short chain hydrocarbons in comparison to long chain hydrocarbons

Answer 8

Lower Boiling Point
Higher volatility
Very Runny (low viscosity)
Higher Flammability

Question 9

what is volatility

Answer 9

the tendency to turn to a gas

Question 10

What is viscosity

Answer 10

how easily it flows

Question 11

Fractional Distillation process of Crude Oil

Answer 11

Crude oil is heated and get in near the bottom of the fractionating column as hot vapour. The column is kept very hot at the bottom and cooler at the top. Different fractions are collected as liquids at different levels in a continuous process

Question 12

What gets collected where in the fractional distillation of crude oil?

Answer 12

Hydrocarbons with smallest molecules have lower boiling points so are collected tse d at the cooler top of the column as gases. At the bottom of the column, fractions have higher boiling points and they cool to form very thick liquids or solids at room temperature

Question 13

Equation for complete combustion of hydrocarbons

Answer 13

Hydrocarbon + Oxygen —> carbon dioxide + water (+energy)

Question 14

How to test for the gases formed in complete combustion of a hydrocarbon

Answer 14

• Carbon dioxide turns limewater cloudy

- Water turns blue cobalt chlorine paper pink OR white anhydrous copper sulfate blue

Question 15

What gas is produced in incomplete combustion of hydrocarbons and why is it bad

Answer 15

Carbon monoxide (CO) is formed. It is a toxic gas which is colourless and odourless. Your red blood cells pick up this gas and carry it round your body instead of oxygen

Question 16

Why are large molecules not good fuels

Answer 16

They are thick liquids/solids with high boiling points. They are difficult to vapourise and don’t burn easily

Question 17

What fuel for modern transport comes from crude oil

Answer 17

Diesel, Kerosene, heavy fuel oil and LPG

Question 18

What does cracking involve

Answer 18

Breaking down larger, longer alkane molecules into smaller more useful ones

Question 19

What is also produced in hydrocarbons cracking

Answer 19

Alkenes which are used as a starting material when making lots of other compounds and can be used to make polymers

Question 20

What type of reaction is cracking

Answer 20

it is a thermal decomposition reaction as it involves breaking down molecules by heating them

Question 21

Explain the cracking process (catalytic and steam cracking)

Answer 21

First the long chan hydrocarbon is heated to vaporise it

• CATALYTIC CRACKING - the vapour is passed over a hot powdered aluminium catalyst and the long-chain molecules split apart on the surface of the catalyst
• STEAM CRACKING - the vapour is mixed with steam and heated to a very high temperature

Question 22

How to test for alkenes or alkanes

Answer 22

Alkenes are generally more reactive than alkanes. A positive test for an alkene is that it reacts with orange bromine water and turns it colourless. Alkanes do not react with bromine water