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Organic Chemistry > Alkanes > Flashcards

Alkanes Flashcards

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1
Q

What is petroleum?

A

A mixture consisting mainly of alkane hydrocarbons.

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2
Q

What is petroleum fraction?

A

A mixture of hydrocarbons with a similar chain length and boiling point range.

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3
Q

Describe fractional distillation?

A

1)Crude oil is heated.
2)Liquids flow to the bottom of the fractionating column.
3)Vapours rise up the fractionating column condensing at different levels as they reach their boiling points.
4)Hydrocarbons with low boiling points are collected near the top of the fractionating column.

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4
Q

The larger the molecule the larger the?

A

VDW forces.

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5
Q

What is cracking?

A

The conversion of large hydrocarbons to smaller hydrocarbons by breaking C-C bonds.

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6
Q

Economic reasons for cracking?

A

Shorter carbon chains are more in demand.
The products of cracking are more valuable than the starting materials.

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7
Q

Why does cracking require high temperatures?

A

It is a chemical process involving the splitting of strong covalent bonds.

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8
Q

What are the two main types of cracking?

A

Thermal
Catalytic

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9
Q

Conditions needed for thermal cracking?

A

High pressure (7000kPa)
High temperature (400-900 degrees celsius)

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10
Q

What does thermal cracking produce?

A

Mostly alkenes and sometimes hydrogen.

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11
Q

Conditions needed for catalytic cracking?

A

Moderate pressure
High temperature (450 degrees celsius)
Zeolite catalyst

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12
Q

What does catalytic cracking produce?

A

Branched and cyclic alkanes.
Aromatic hydrocarbons.

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13
Q

What are products from thermal cracking used for?

A

Haber process

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14
Q

What are products from catalytic cracking used for?

A

Making motor fuels

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15
Q

Why is catalytic cracking cheaper than thermal cracking?

A

Saves energy as lower temperatures and lower pressure is used.

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16
Q

What is fuel?

A

Releases heat energy when burnt.

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17
Q

What is complete combustion?

A

In excess, oxygen alkanes will burn with complete combustion.

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18
Q

What are the products of complete combustion?

A

H20 and CO2.

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19
Q

What is incomplete combustion?

A

Limited amount of oxygen will cause incomplete combustion and the production of CO and/or C.

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20
Q

What can carbon cause?

A

Carbon (soot) can cause global dimming, reflection of the sun’s light.

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21
Q

Sulfur Dioxide equation?

A

S + O2 -> SO2

22
Q

How does acid rain happen?

A

Sulfur dioxide will dissolve in atmospheric water.

23
Q

How can sulfur dioxide be removed from waste gases from furnaces?

A

Flue gas desulfurisation.

24
Q

Desulfurisation equation?

A

SO2 + CaO –> CaSO3

25
Q

How do nitrogen oxides form?

A

From the reaction between N2 and O2 inside the car engine. High temperature and spark provide sufficient energy to break the N2 bond.

26
Q

Environmental consequences of NO?

A

Toxic and can form acidic gas NO2

27
Q

Environmental consequence of NO2?

A

Toxic and acidic and forms acid rain.

28
Q

What do catalytic converters do?

A

They remove CO and NO and unburned hydrocarbons from exhaust gases turning them into harmless CO2, N2 and H2O.

29
Q

Why do catalytic converters have a ceramic
honeycomb coated with a thin layer of catalyst metals platinum, palladium, rhodium?

A

To increase surface area.

30
Q

3 greenhouse gases?

A

Methane, Carbon Dioxide and Water Vapour.

31
Q

Greenhouse effect explained?

A

UV radiation passes through the atmosphere to the Earth’s surface and heats up the earth’s surface.
The earth radiates out infrared long wavelength radiation. The C=O bonds in CO2 absorb infrared radiation so the IR radiation doesn’t escape from the atmosphere.

32
Q

Why have CO2 levels increased?

A

Increased burning of fossil fuels.

33
Q

What condition is needed for free radical substitution?

A

UV light.

34
Q

Why dont alkanes react
with many reagents?

A

The C-C bond and the C-H bond are relatively strong.

35
Q

3 steps for free radical substitution?

A

1)Initiation
2)Propagation
3)Termination

36
Q

Why is the UV light required?

A

It provides energy to break the Cl-Cl bond. It is broken in preference to others as it is the weakest.

37
Q

What do we call the process of Cl2 breaking into Cl- and Cl-?

A

Homolytic fission

38
Q

Do free radicals have a charge?

A

No

39
Q

Define free radical?

A

A free radical is a reactive species which
possess an unpaired electron.

40
Q

Why are high temperatures necessary for cracking reactions to occur?

A

To break the bonds.

41
Q

Why is thermal cracking carried out in industry?

A

To make products which are in great demand.

42
Q

Why is CO2 an environmental problem?

A

Causes global dimming
Smog

43
Q

How can the CIP priority rules be used to deduce the full IUPAC name of the compound.

A

1)Consider the atomic number of the atoms attached.
2) The one with the higher atomic number takes priority.
3)Both groups contain the same atom so consider atoms one bond further away.
4)One group takes priority over the other as it has a higher atomic number.
5) Deduce whether it is E or Z isomerism.
6) State the name of the compound.

44
Q

Give an equation for a reaction that removes nitrogen monoxide in a
catalytic converter.

A

2 NO + 2 CO → N2 + 2 CO2

45
Q

Testing for alkanes/alkenes?

A

Bromine water
Alkane - remains same colour
Alkene - brown to colourless.

46
Q

Why do oil companies need to crack suitable heavy fractions?

A

Long chain hydrocarbons are broken into smaller chain hydrocarbons by using a catalyst such as zeolite. Smaller chain molecules are more in demand.

47
Q

Complete combustion of C8H18?

A

C8H18 + O2 -> CO2 + H2O

48
Q

Incomplete combustion of C8H18?

A

C8H18 + O2 -> CO + H2O

49
Q

How are oxides of nitrogen formed?

A

Nitrogen reacts with oxygen from the air at high temperatures.

50
Q

Two products obtained by catalytic cracking?

A

Aromatic hydrocarbons
Branched Alkanes

51
Q
A

Organic Chemistry (2 decks)

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