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Alkanes and Crude Oil Flashcards

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1
Q

What happens to the boiling point of alkanes as the carbon chain length increases?

A

The boiling point increases due to stronger van der Waals’ forces between molecules.

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2
Q

Why do longer carbon chains result in higher boiling points for alkanes?

A

Because there are more electrons in the molecules, leading to stronger van der Waals’ forces.

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3
Q

What is the relationship between branched carbon chains and unbranched carbon chains and their boiling points?

A

The more branched the carbon chain, the lower the boiling point.

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4
Q

Why do branched alkanes have lower boiling points compared to their straight-chain isomers?

A

Due to weaker van der Waals’ forces between molecules, as they cannot pack as close together.

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5
Q

What are the primary natural resources formed from the slow decay of marine animals and plants?

A

Crude oil and natural gas

Formed over millions of years under heat and pressure in the absence of air.

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6
Q

What is the main composition of crude oil?

A

A complex mixture consisting mainly of alkanes, cycloalkanes, some aromatics, and other compounds containing sulfur and oxygen

The exact composition varies around the world.

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7
Q

Why is crude oil not useful in its raw form?

A

It must be partly separated and modified to provide useful products

This is necessary to utilize its components effectively.

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8
Q

What method is used to separate the components of crude oil?

A

Fractional distillation

This method takes advantage of the differences in boiling points of the compounds.

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9
Q

What are the steps involved in the fractional distillation of crude oil?

A
  1. Crude oil is vaporised
  2. Vapour is passed into a tower that is hot at the bottom and cold at the top
  3. Vapour cools as it rises
  4. Molecules condense at different heights based on boiling points

Larger molecules with higher boiling points condense lower down the column.

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10
Q

True or False: All crude oils have the same composition.

A

False

The composition of crude oils varies around the world.

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11
Q

Fill in the blank: The larger the molecule, the ______ it condenses in the fractional distillation column.

A

lower down

This is due to higher boiling points of larger molecules.

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12
Q

What is a fraction?

A

A mixture of hydrocarbons with similar boiling points

Fractions are produced during the distillation of crude oil.

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13
Q

As the C chain gets longer, what happens to hydrocarbons?

A

They become:
* more viscous
* harder to ignite
* less volatile
* have higher boiling points

These changes affect the physical properties and usability of hydrocarbons.

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14
Q

What is contained in the residue from the primary distillation?

A

Useful substances such as:
* fuel oil
* lubricating oil
* waxes
* bitumen

These substances boil above 350°C at atmospheric pressure.

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15
Q

Fill in the blank: The residue from the primary distillation contains useful substances that boil above _______.

A

350°C

This is at atmospheric pressure.

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16
Q

What is the purpose of distillation at lower pressure?

A

To separate substances that decompose above 350°C

At lower pressure, boiling points are lowered, allowing separation without decomposition.

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17
Q

What are the characteristics of petroleum fractions with shorter C-chains?

A

They are better fuels than those with longer C-chains

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18
Q

What is the demand situation for petroleum fractions with shorter C-chains?

A

Greater demand than supply

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19
Q

What is the supply situation for petroleum fractions with longer C-chains?

A

Greater supply than demand

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20
Q

What process is used to address the supply-demand imbalance for shorter alkanes?

A

Cracking

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21
Q

What is cracking?

A

The thermal decomposition of alkanes to produce higher value shorter C-chain products

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22
Q

What type of chemical bonds are broken during the cracking process?

A

C-C bonds

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23
Q

Fill in the blank: Cracking is done to make use of excess fractions with _______ C-chains.

24
Q

What type of catalyst is used in Thermal cracking?

Study These Flashcards
A

No catalyst is used

25
What is the temperature for thermal cracking?
900°C ## Footnote Thermal cracking operates at high temperatures to break down hydrocarbons.
26
What is the pressure used in catalytic cracking?
1-2 atm ## Footnote Catalytic cracking typically operates at lower pressures compared to thermal cracking.
27
What type of catalyst is used in catalytic cracking?
zeolites (a type of aluminosilicate catalyst) ## Footnote Zeolites are known for their porous structure and catalytic properties.
28
What are the main products of Catalytic cracking?
motor fuels (cyclic alkanes, branched alkanes, aromatics) ## Footnote These products are essential for fuel and chemical industries.
29
What is the temperature for catalytic cracking?
450°C ## Footnote Catalytic cracking occurs at lower temperatures compared to thermal cracking.
30
What pressure is used in thermal cracking?
70 atm ## Footnote This high pressure facilitates the breaking of larger hydrocarbon molecules.
31
What type of products does thermal cracking primarily yield?
alkenes ## Footnote Alkenes are important building blocks in the chemical industry.
32
What is CO2 and how is it formed?
Complete combustion of fuels containing carbon ## Footnote CO2 is a greenhouse gas that contributes to global warming.
33
What problem does CO2 cause?
Greenhouse gas contributing to climate change ## Footnote CO2 traps heat in the atmosphere.
34
What is CO and how is it formed?
Incomplete combustion of fuels containing carbon ## Footnote CO is toxic and can cause health issues.
35
What problems does C (soot) cause?
Blackens buildings, can cause respiratory problems, global dimming
36
What is H2O and how is it formed?
Combustion of fuels containing hydrogen ## Footnote H2O is not considered a pollutant.
37
What is SO2 and how is it formed?
Combustion of sulfur-containing compounds in fuel
38
How are nitrates formed?
Reaction of nitrogen (N2) in the air with oxygen (O2) at very high temperatures ## Footnote NOx includes NO and NO2, contributing to acid rain.
39
What problem do nitrates cause?
Acid rain ## Footnote Acid rain can harm ecosystems and structures.
40
How are unburned hydrocarbons formed?
Some of the fuel may not actually burn ## Footnote Unburned hydrocarbons contribute to air pollution.
41
Name a method to reduce CO2 emissions.
Burn less fossil fuels ## Footnote Reducing fossil fuel use can decrease CO2 output.
42
What is one way to ensure more complete combustion when burning fuels?
Ensure a good supply of oxygen ## Footnote Adequate oxygen helps achieve more efficient combustion.
43
How can sulfur dioxide (SO2) emissions be reduced?
Remove sulfur from fuel before burning, flue gas desulfurisation ## Footnote Desulfurization processes can significantly lower SO2 emissions.
44
What is the function of catalytic converters in cars?
To reduce the amount of nitrates released in our atmosphere ## Footnote Catalytic converters convert pollutants into less harmful substances.
45
How to reduce the amount of unburned hydrocarbons?
Ensure engines are well-tuned and there is a good supply of oxygen ## Footnote Well-tuned engines operate more efficiently and produce fewer emissions.
46
Why is CO problematic?
It is toxic
47
Why is SO2 a problem?
SO2 can lead to acid rain.
48
What are greenhouse gases?
Gases that absorb the IR radiation given off by the Earth, but do not absorb higher frequency UV/visible radiation from the sun.
49
Which types of bonds in molecules absorb IR radiation?
Polar bonds.
50
Name three greenhouse gases.
* CO2 * H2O * CH4
51
Why are N2 and O2 not considered greenhouse gases?
They do not absorb IR radiation and lack polar bonds.
52
What do most scientists believe is causing the Earth's warming?
Increasing amounts of greenhouse gases in the atmosphere.
53
What is a significant source of carbon dioxide in the atmosphere?
The burning of fossil fuels.
54
How have carbon dioxide levels changed in recent years?
They have risen significantly.
55
What agricultural practice has contributed to the increase in methane levels?
Farming.
56
Fill in the blank: CO2 and CH4 are examples of _______.
[greenhouse gases]
57
True or False: CH4 has polar C-H bonds.
True.

Organic Chem (1 decks)

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