Paper 1 - Crude Oil and Alkanes

Question 1

What is a hydrocarbon?

Answer 1

Hydrocarbons are molecules that are formed of hydrogen and carbon atoms only

Question 2

What is the general formula for alkanes?

Answer 2

CnH2n+2

Question 3

What are the first 6 alkanes?

Answer 3

Methane
Ethane
Propane
Butane
Pentane
Hexane

Question 4

What happens when fuel is burned?

Answer 4

Heat energy is released

Question 5

How do SO2 and N02 contribute to acid rain?

Answer 5

• SO2/N02 react with H2O in clouds and form sulphuric/nitric acid
• this acid (acid rain), falls upon towns, corroding, buildings, and statues and killing plants by firming the soil

Question 6

How does industrial process of fractional distillation, separate crude oil into fractions?

Answer 6

1. crude oil is heated to 350°C to vaporise it.
2. Gases and fractionates in column at the bottom.
3. The gradient is exists: the tower is cooler at the top and hotter at the bottom.
   4 vapours condensed back into liquids at their boiling points, different fractions have different boiling points, and collect at different levels of the tower
4. Small chain hydrocarbons have low boiling points and collect as gas at the top of the column where temperature is lower.
5. Long chain hydrocarbons have high boarding points and collecting near the bottom of the tower where temperature is higher 

Question 7

What is the impact of carbon monoxide?

Answer 7

• It is poisonous
• It replaces the oxygen in the blood with carbon
• Cells cannot aerobically respire
• Leads to: fainting, comas or death

Question 8

What is the homologous series?

Answer 8

“Family” of hydrocarbons that all have similar chemical properties

Question 9

How is crude oil formed and what of?

Answer 9

• microscopic plants, animals (plankton) that die and fall to the seabed
• Layers of sand and mud from on top
• Pressure and high temperatures cause oil to form
• Oil is obtained by drilling into seabed

Question 10

Why are alkanes classified as saturated hydrocarbons?

Answer 10

• Alkanes do not have a double bond
• Alkanes have the maximum possible number of hydrogen atoms

Question 11

What is the reaction between alkanes and halogens in the presence of UV radiation?

Answer 11

• This is known as a substitution reaction
• A halogen reacts with an alkane to form a haloalkane
• One hydrogen atom is replaced with a halogen atom

Question 12

What does crude oil contain?

Answer 12

A mix of hydrocarbons

Question 13

How is burning of hydrocarbons classified as a combustion reaction and what can it be used for?

Answer 13

• A reaction that burns a substance, releasing heat energy
• Useful for electricity, heating and transport
• Hydrocarbon + O2 —> CO2 + H2O

Question 14

Draw the molecular structure of pentane

Answer 14

Draw it then google it

Question 15

How are hydrocarbons represented?

Answer 15

• empirical formula (simplest)
• Molecular formula (actual molecular structure)
• Structural formula
• Displayed formula

Question 16

How do you test for CO2?

Answer 16

• Below CO2 into clear lime water
• If limewater turns, cloudy, CO2 is present

Question 17

What is an isomer?

Answer 17

Molecule with the same molecular formula as another molecule, but with a different displayed formula

Question 18

What are the main uses for the fractions obtained from crude oil?

Answer 18

• Refinery gases - domestic heating
• Gasoline - fuel for petrol cars
• Kerosene - plane fuel
• Diesel oil - cars, lorries, vans
• (Heavy) fuel oil - ships
• Bitumen - repairing and laying tarmac

Question 19

What are the properties of long chain hydrocarbons?

Answer 19

• High boiling point
• Low flammability
• High viscosity

Question 20

What are the properties of short chain hydrocarbons?

Answer 20

• Low boiling point
• High flammability
• Low viscosity

Question 21

What are the main fractions that are obtained from crude oil?

Answer 21

Coldest/Top:

• Refinery gases
• Gasoline (Petrol)
• Kerosene
• Diesel oil
• (Heavy) fuel oil
• Bitumen

Hottest/Bottom:

Question 22

What is the trend in colour, boiling point and viscosity of the main fractions?

Answer 22

As the hydrocarbon chains become longer: the boiling point increases, viscosity increases and colour becomes darker

Question 23

How do you test for alkenes and alkanes?

Answer 23

• Use bromine water (initially orange)
• Add hydrocarbon solution
• If solution turns, colourless, hydrocarbon is an alkene
• A solution remains orange, hydrocarbon is an alkane

Question 24

What is a functional group?

Answer 24

Specific group of atoms or bonds within a molecule that is responsible for characteristics in chemical reactions

Question 25

Give an example of isomers

Answer 25

Butane and cyclobutane

(both C4H8)

Question 26

In car engines, what is the temperature high enough to do?

Answer 26

To allow nitrogen and oxygen from the air to react, forming oxides of nitrogen such as NO2 or NO

Question 27

How was the reaction classified as a substitution reaction?

Answer 27

• Halogens react with alkanes to make haloalkanes
• UV light is needed
• One hydrogen atom is replaced by a halogen atom
• e.g. methane + bromine —> bromomethane + hydrogen bromide

Question 28

How does the combustion of sulphur impurities and hydrocarbon fuels result in the formation of sulphur dioxide?

Answer 28

• Impure hydrocarbons are burned and sulphur is produced
• Sulphur impurities react with oxygen in the air, forming sulphur dioxide

Question 29

What are the products of complete combustion?

Answer 29

Carbon dioxide and water

Question 30

What are the products of incomplete combustion?

Answer 30

Carbon monoxide, soot and water