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Chemistry > Crude oils and fuels (7.1) (M) > Flashcards

Crude oils and fuels (7.1) (M) Flashcards

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1
Q

What type of resource is crude oil?

A

A finite resource

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2
Q

Where is crude oil found?

A

in rocks

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3
Q

What is physically crude oil?

A

Crude oil is the remains of an ancient biomass consisting mainly of plankton that was buried in mud

+ include ‘a finite resource found in rocks’ and maybe chemical composition

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4
Q

What is the chemical composition of crude oil?

A

a mixture of a very large number of compounds

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5
Q

What are most of the oils found in crude oil?

A

hydrocarbons

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6
Q

What are hydrocarbons?

A

molecules made up of hydrogen and carbon atoms only

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7
Q

What makes up most of the hydrocarbons found in crude oil?

A

alkanes

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8
Q

What is the general formula for the homologous series of alkanes?

A

CnH2n+2

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9
Q

What are the first four members of the alkanes?

A

methane (CH4), ethane (C2H6), propane (C3H8) and butane (C4H10)

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10
Q

What are the two forms alkanes can be represented in? (formula and diagram)

A

example for ethane

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11
Q

What are many hydrocarbons in crude oil may be separated into?

A

fractions

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12
Q

What are fractions?

A

mixtures of hydrocarbons which contain molecules with a similar number of carbon atoms, separated by fractional distillation

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13
Q

What can fractions be processed to do?

A

produce fuels and feedstock for the petrochemical industry

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14
Q

5 needed

What are some fuels produced from crude oil we depend our modern lifestyle on?

A
  • petrol
  • diesel oil
  • kerosene (jet fuel)
  • heavy fuel oil
  • liquefied petroleum gases
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15
Q

Many useful materials on which modern life depends are produced by what industry?

A

the petrochemical industry

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16
Q

4 needed

What are examples of useful materials on which modern life depends produced the petrochemical industry

A

solvents, lubricants, polymers, detergents

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17
Q

The vast array of natural and synthetic carbon compounds occur due to what?

A

the ability of carbon atoms to form families of similar compounds

18
Q

Explain how fractional distillation separates crude oil into fractions

A
  • Crude oil enters a tall fractionating column, which is hot at the bottom and gets cooler towards the top
  • The crude oil is heated
  • to evaporate the hydrocarbons
  • vapours from the oil rise through the column
  • hydrocarbons condense when cool enough
  • at their different boiling points
  • and collected as fractions (each fraction has a different boiling point based on the length of the hydrocarbon chain/molecule)
  • smaller hydrocarbons collected at top, larger hydrocarbons collected at bottom (longest ones i.e. bitumen will not evaporate and is collected as residue)
19
Q

How do smaller hydrocarbons compare with large hydrocarbons in terms of the properties: boiling point, flammability, viscocity and smokiness of flame?

A

Smaller hydrocarbons:

  • have lower boiling points
  • are more flammable
  • have a lower viscosity
  • the flame is also cleaner (less smoky) - due to higher flammability
20
Q

What does the combustion of hydrocarbon fuels release?

A

energy

21
Q

What happens to the carbon and hydrogen in the fuels (hydrocarbons) during combustion?

A

They are oxidised (gain of oxygen)

22
Q

What does the complete combustion of a hydrocarbon produce?

A

carbon dioxide and water

23
Q

What does combustion require?

A

heat

24
Q

What is the formula for the complete combustion of ethene?

A

C2H4 + 3O2 ⇢ 2CO2 + 2H2O

25
Q

What is cracking?

A

the process of breaking down larger, less useful hydrocarbons to produce smaller, more useful molecules

26
Q

What are 2 forms of cracking?

A

catalytic cracking and steam cracking

27
Q

What are the conditions required for catalytic cracking?

A

passing large hydrocarbon vapour (may be soaked in ceramic wool) over a hot catalyst (e.g. porous broken pot).

Heat to very high temperature

only bold is necessary

28
Q

What are the conditions required for steam cracking?

A

mixing large hydrocarbon vapour with steam and heating to a very high temperature

only bold is necessary

29
Q

What are the products of cracking?

A

alkanes (saturated) and alkenes (unsaturated)

30
Q

What are more reactive, alkanes or alkenes?

A

alkenes

31
Q

How do you test for an alkene?

A

Add orange bromine water to hydrocarbon, if it turns colourless, an alkene is present

(alkenes react with bromine water, alkanes do not)

32
Q

Which fuels are in high demand?

A

small molecules (hydrocarbons)

crude oil contains too many large hydrocarbons and not enough smaller, more useful ones

33
Q

Some of the products of cracking are used as (…) as small molecules (hydrocarbons) are in high demand

A

fuels

34
Q

2 needed

What are the uses of alkenes?

A
  • produce polymers
  • used as starting materials for the production of many other chemicals
35
Q

What is the reaction for the cracking of C6H14?

A

C6H14 ⇢ C4H10 + C2H4

36
Q

Alkenes turn bromine water from (…) to (…)

A

brown

colourless

  • so bromine water is test for alkenes (no affect on alkanes)*
  • as alkenes react with bromine by breaking their carbon-carbon double bond*
37
Q

What are two conditions needed for cracking?

A
  • High temperature
  • Catalyst or steam
38
Q

Why does cracking take place?

A

To obtain smaller hydrocarbon molecules

that are in demand

and are more useful/are used as fuels

39
Q

After cracking, a black substance is produced on the bottom of the beaker. What is this and why is it produced?

A

Soot

produced by incomplete combustion

40
Q

The demand for smaller hydrocarbon fraction high and supply is low, suggest 3 ways to how the oil industry could overcome this problem

A
  • cracking
  • use different/lighter crude oils
  • development new techniques to use low demand fractions (or hydrocarbons depending on question) as fuels
41
Q

What does volatile mean?

A

Evaporates easily/quickly

Chemistry (34 decks)

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