C7

Question 1

What are hydrocarbons?

Answer 1

Compounds formed from carbon and hydrogen atoms only.

Question 2

What is the general formula for alkanes?

Answer 2

CₙH₂ₙ₊₂

Question 3

What types of bonds do alkanes have?

Answer 3

C-C and C-H single bonds.

Question 4

List the first four alkanes.

Answer 4

• Methane (CH₄)
• Ethane (C₂H₆)
• Propane (C₃H₈)
• Butane (C₄H₁₀)

Question 5

What occurs during complete combustion of hydrocarbons?

Answer 5

Release of energy with carbon dioxide and water vapour as waste products.

Question 6

What is the balanced equation for the complete combustion of methane?

Answer 6

CH₄ + 2O₂ → CO₂ + 2H₂O

Question 7

What is oxidation in the context of combustion?

Answer 7

Gain of oxygen.

Question 8

What are the waste products of complete combustion?

Answer 8

Carbon dioxide and water vapour.

Question 9

Fill in the blank: The complete combustion of a hydrocarbon in oxygen releases lots of _______.

Answer 9

[energy]

Question 10

What is crude oil formed from?

Answer 10

Remains of ancient marine organisms.

Question 11

What are non-renewable resources?

Answer 11

Resources that take longer to form than to be consumed.

Question 12

What are some important uses of hydrocarbons?

Answer 12

• Fuels
• Plastics
• Lubricants
• Detergents

Question 13

True or False: The longer the carbon chain in hydrocarbons, the more runny they are.

Answer 13

False

Question 14

What happens to the boiling points of hydrocarbons as the carbon chain length increases?

Answer 14

They increase.

Question 15

What is a homologous series?

Answer 15

A series of compounds containing similar functional groups.

Question 16

Fill in the blank: Hydrocarbons only contain two ingredients - carbon and _______.

Answer 16

[hydrogen]

Question 17

Write a balanced symbol equation for the complete combustion of ethane, C₂H₆.

Answer 17

C₂H₆ + 7/2 O₂ → 2 CO₂ + 3 H₂O

Question 18

What happens to the flammability of hydrocarbons as the carbon chain length increases?

Answer 18

It generally decreases.

Question 19

What is crude oil primarily composed of?

Answer 19

Hydrocarbons

Hydrocarbons are compounds made up of hydrogen and carbon atoms.

Question 20

What are plankton?

Answer 20

Tiny plants and animals in oceans and large bodies of water

Plankton serve as the primary source of organic matter in the ocean, contributing to the formation of crude oil.

Question 21

What is a feedstock?

Answer 21

A raw material used for a chemical process

Feedstocks are essential for producing various chemicals and materials, including plastics.

Question 22

What happens to the properties of hydrocarbons as the chain gets longer?

Answer 22

Properties change, becoming less viscous and having lower boiling points

Longer hydrocarbon chains generally lead to increased runniness and flammability.

Question 23

True or False: Crude oil is an infinite resource.

Answer 23

False

Crude oil is finite, meaning it is limited in quantity and cannot be replenished on a human timescale.

Question 24

What is the relationship between viscosity and boiling point in hydrocarbons?

Answer 24

Higher viscosity corresponds to higher boiling points

More viscous hydrocarbons tend to have higher boiling points compared to less viscous ones.

Question 25

Fill in the blank: Crude oil can be processed to create a variety of products, including _______.

Answer 25

Plastics ## Footnote Plastics are derived from the chemical processing of crude oil, showcasing its versatility.

Question 26

What are homologous series?

Answer 26

Groups of hydrocarbons with similar properties ## Footnote Homologous series consist of compounds that differ by a specific structural unit, such as a -CH2- group.

Question 27

What is the significance of crude oil in everyday life?

Answer 27

It is essential for making many important products, like plastics ## Footnote Without crude oil, many modern conveniences, such as plastic pens, would not exist.

Question 28

What does it mean when we say crude oil is finite?

Answer 28

It means that crude oil is a limited resource ## Footnote Finite resources cannot be replaced once consumed, highlighting the need for sustainable alternatives.

Question 29

What is fractional distillation?

Answer 29

A process to separate compounds in crude oil by heating and cooling to isolate different fractions based on boiling points.

Question 30

How does fractional distillation work?

Answer 30

The oil is heated to evaporate most of it, enters a fractionating column, and is then cooled as it rises, allowing different hydrocarbons to condense at various heights.

Question 31

What happens to shorter hydrocarbons during fractional distillation?

Answer 31

They have low boiling points, rise near the top of the column, and remain as gases at low temperatures.

Question 32

Where do longer hydrocarbons condense in a fractionating column?

Answer 32

They condense back into liquids and drain out of the column lower down where the temperature is higher.

Question 33

What is the relationship between carbon atoms and boiling points in hydrocarbons?

Answer 33

Hydrocarbons in the same fraction have a similar number of carbon atoms, leading to similar boiling points.

Question 34

True or False: Petrol drains further up a fractionating column than diesel.

Answer 34

True

Question 35

Fill in the blank: The boiling point of petrol is ______ than that of diesel.

Answer 35

lower

Question 36

What is cracking in organic chemistry?

Answer 36

A process that breaks down long-chain hydrocarbons into smaller molecules, including alkenes.

Question 37

What are the two methods of cracking?

Answer 37

Catalytic cracking and steam cracking.

Question 38

What is the result of adding bromine water to an alkene?

Answer 38

The bromine water turns from orange to colorless.

Question 39

What is steam cracking?

Answer 39

A method where long-chain hydrocarbons are heated and mixed with steam to produce smaller molecules.

Question 40

What is the significance of balancing chemical equations in cracking?

Answer 40

To ensure the number of carbon and hydrogen atoms is conserved during the reaction.

Question 41

What is an example of a hydrocarbon that can be cracked?

Answer 41

Decane.

Question 42

What is the formula for pentane?

Answer 42

C5H12

Question 43

Fill in the blank: Cracking is a type of ______ decomposition reaction.

Answer 43

thermal

Question 44

What is the approximate number of carbon atoms in LPG (Liquefied Petroleum Gas)?

Answer 44

3 to 4

Question 45

What type of hydrocarbons does heavy fuel oil contain?

Answer 45

Long-chain hydrocarbons.

Question 46

What is bitumen in the context of fractional distillation?

Answer 46

The residue left after all other fractions have been distilled off.

Question 47

What is the process of breaking down long-chain hydrocarbons into smaller molecules called?

Answer 47

Cracking ## Footnote Cracking can be performed through methods like steam cracking and catalytic cracking.

Question 48

What are the two main methods of cracking hydrocarbons?

Answer 48

* Steam cracking * Catalytic cracking ## Footnote Each method has distinct processes; steam cracking involves mixing hydrocarbon vapour with steam and heating, while catalytic cracking uses catalysts to speed up the reaction.

Question 49

In steam cracking, what is mixed with hydrocarbon vapour before heating?

Answer 49

Steam ## Footnote This mixture is then heated to a very high temperature to split the hydrocarbons.

Question 50

What role do catalysts play in catalytic cracking?

Answer 50

They speed up reactions without getting used up ## Footnote Catalysts allow the cracking process to occur more efficiently.

Question 51

What substance is typically used as a catalyst in catalytic cracking?

Answer 51

Powdered aluminium oxide ## Footnote The vapour of long-chain hydrocarbons is passed over this catalyst.

Question 52

Complete the equation: C10H22 → C8H18 + ....

Answer 52

C2H4 ## Footnote The missing product is determined by balancing the number of carbon and hydrogen atoms on each side.

Question 53

True or False: The number of carbon atoms in the missing product equals the number of carbons in C10H22 minus the number of carbons in C8H18.

Answer 53

True ## Footnote This is a key step in balancing the equation for cracking reactions.

Question 54

How many hydrogen atoms would be in the missing product if C10H22 is cracked to form C8H18?

Answer 54

4 ## Footnote This is calculated by subtracting the number of hydrogens in C8H18 from those in C10H22.

Question 55

What is the product of cracking pentane, C5H12?

Answer 55

Ethene and one other hydrocarbon ## Footnote The balanced symbol equation for this reaction would need to be determined based on the products formed.

Question 56

Fill in the blank: The process of cracking is important because it allows us to use all the long-chain hydrocarbons we otherwise _______.

Answer 56

wouldn't need ## Footnote Cracking helps to utilize hydrocarbons that are less useful in their original form.

Question 57

What is the first step in the steam cracking process?

Answer 57

Heating long-chain hydrocarbons to turn them into a gas ## Footnote This is essential before mixing with steam for further processing.