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Chemistry AS > Alkanes > Flashcards

Alkanes Flashcards

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1
Q

Are alkanes a homologus series of saturated or unsaturated hydrocarbons?

A

Saturated.

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2
Q

What is the same in all alkanes?

A

Functional group and general formula.

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3
Q

What is similar in all alkanes?

A

Their chemical proeprties.

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4
Q

What does each alkane differ by one group of?

A

Ch2

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5
Q

How are alkanes produced?

A

Through the fractional distillation of crude oil ad the hydrogenation of alkenes.

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6
Q

What are branched chain alkanes?

A

Alkanes which have side groups which are attached to the main carbon chain.

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7
Q

What are cyclic alkanes?

A

Alkanes which have their carbons connected to form a ring shape.

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8
Q

What are structural isomers?

A

Where the molecule has the same molecular formula but a different structul formula.

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9
Q

Why are cycloalkanes not isomers of straight chain alkanes?

A

This is because they have different formulae, instead they are isomers of alkenes.

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10
Q

What happens as alkane chains get longer?

A

Their boiling point increase.

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11
Q

Why does the boiling point of alkanes increase as alkane chains get longer?

A

The intermolecular forces increase meaning that more energy is required to overcome them and cause a change of state from liquid to gas.

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12
Q

Why are alkanes relatively unreactive?

A

They have strong carbon-carbon single bonds and strong carbon-hydrogen bonds.

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13
Q

What reactions do alkanes undergo?

A

Combustion, cracking and halogenation.

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14
Q

What is the equation for complete combustion using alkanes?

A

Alkane + Oxygen -> Cabron Dioxide + Water

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15
Q

What are the two equations for incomplete combustion using alkanes?

A

Alkane + Oxygen -> Carbon Monoxide + Water
Alkane + Oxygen -> Carbon + Water

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16
Q

Why are smaller chain alkanes in high demand?

A

They are most commonly used for heating, cooking, transportation and energy generation.

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17
Q

Why do large chain alkanes get cracked?

A

To produce shorter chain alkanes which are in high demand compared to the amount that we have.

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18
Q

What is halogenation?

A

This is where a hydrogen atom on the alkane gets replaced by a halogen atom in order to form a halogenoalkane.

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19
Q

What are arenes?

A

Compounds with a benzene ring.

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20
Q

What are the type of hydrocarbons in crude oil?

A

Alkanes, cycloalkanes and arenes.

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21
Q

What are the two types of cracking?

A

Thermal and catalytic.

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22
Q

What is thermal cracking?

A

The use of high pressure and temperature to produce alkanes and alkenes.

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23
Q

What is catalytic cracking?

A

The use of a lower temperature and pressure with a catalyst present to produce mainly aromatic hydrocarbons.

24
Q

Is cracking endothermic or exothermic?

A

Endothermic.

25
Q

At what temperature is crude oil first vaporised at during fractional distillation?

A

350 degrees celsius.

26
Q

Why are alkanes almost non-polar?

A

Their electrongeativities are so similar. They have only van der waals forces.

27
Q

What type of intermolecular forces do alkanes have?

A

Van der waals forces only.

28
Q

Why are alkanes insoluble in water?

A

In water, the molecules are held together by hydrogen bonds which is much stronger than the alkanes van der waals forces.

29
Q

What is the function of fractional distilltion?

A

To seperate crude oil into it’s useful products.

30
Q

What do shorter alkanes produce when burnt completely in a plentiful supply of oxygen?

A

Carbon dioxide and water.

31
Q

What are the products of incomplete combustion?

A

Carbon monoxide and water. Somtimes soot too.

32
Q

What are the gases given out by power stations called?

A

Flue gases.

33
Q

What is one of the products of the burning of fossil fuels during the generation of electricity?

A

Sulfur dioxide.

34
Q

What is the removal of sulfur dioxide called?

A

Flue gas desulfuration.

35
Q

What is one flue gas desulfuration method?

A

A lurry of calcium oxide and water is sprayed onto the flue gas, this reacts to form calcium sulfite which can be further oxidised to form caclium sulfate.

36
Q

What is calcium sulfate also known as?

A

Gypsum.

37
Q

What is the flue gas desulfurisation reaction?

A

CaO (s) + 2H20 (l) + SO2 (g) + 0.5 O2 -> CaSO4 .2H20

38
Q

What is a catalytic converter?

A

A honeycombe made of ceramic material coated with platinum and rhodium metals which are catalysts, they reduce the output of of carbon monoxide, nitrogen oxides and unburnt hydrocarbons in the exhaust mixture.

39
Q

Why is carbon dioxide bad for the environment in excess?

A

It traps infrared radiation within the earth’s atmosphere and causes it to heat up.

40
Q

Why does the greenhouse gas water vapour stay roughly the same?

A

Due to the equilibrium that exists between water vapour and liquid water, however as the earth warms up there will be more vapour in the air and the equilibrium will shift.

41
Q

What type of process is fractional distillation?

A

A physical process.

42
Q

What can crude oil also contain other than hydrocarbons?

A

Sulfur.

43
Q

How can fractional distillation contribute to acid rain?

A

Crude oil can contain sulfur which when burned produces sulfur dioxide which helps to cause acid rain.

44
Q

What are alkanes?

A

Hydrocarbons that can be produced by the addition reaction of hydrogen to an alkene or by cracking of longer alkane chains.

45
Q

What are the two types of cracking?

A

Thermal and catalytic.

46
Q

What does the chamber for cracking not contain and why?

A

Oxygen to prevent combustion.

47
Q

What happens when a larger hydrocarbon is cracked?

A

A smaller alkane and one or more alkene molecules are formed.

48
Q

What does thermal cracking require?

A

High temperatures and pressure.

49
Q

What is mainly produced with thermal cracking?

A

Alkanes and a lot of alkenes.

50
Q

What does catalytic cracking require?

A

Lower temperature than thermal and a slight pressure as well as a catalyst such as zeolite or aluminium oxide.

51
Q

What is mainly produced with catalytic cracking?

A

Aromatic hydrocarbons.

52
Q

What happens when alkanes are burnt in excess oxygen?

A

Complete combustion occurs.

53
Q

What does the incomplete combustion of alkanes create?

A

Carbon monoxide and water.

54
Q

Where is one of the places incomplete combustion takes place?

A

Inside a car engine.

55
Q

Why is carbon monoxide toxic and dangerous?

A

It binds well to haemoglobin which therefore cannot bind to oxygen and carbon dioxide.

56
Q
A

Chemistry AS (16 decks)

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