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GCSE Chemistry > C9 - Crude Oils & Fuels > Flashcards

C9 - Crude Oils & Fuels Flashcards

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1
Q

What is an alkane?

A

A saturated hydrocarbon with the general formula CₙH₂ₙ₊₂, for example, methane, ethane, propane

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2
Q

What is an alkene?

A

Unsaturated hydrocarbon, which contains a carbon-carbon double bond. Its general formula is CₙH₂ₙ, for example, ethene C₂H₄

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3
Q

What is cracking?

A

the reaction used in the oil industry to break down long-chain hydrocarbons into shorter-chain, more useful hydrocarbons

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4
Q

What is distillation?

A

Separation of a liquid from a mixture by evaporation followed by condensation

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5
Q

What is a double bond?

A

A covalent bond made by the sharing of 2 pairs of electrons

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6
Q

What does flammable mean?

A

easily ignited and capable of burning rapidly

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7
Q

What is a fraction?

A

Hydrocarbons with similar number of carbon atoms and boiling points separated from crude oil

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8
Q

What is fractional distillation?

A

A way to separate liquids from a mixture of liquids by boiling off the substances at different temperatures, then condensing and collecting the liquids

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9
Q

What is a general formula?

A

A formula that represents the common structure of all compounds in a single class of chemicals, For example, the general formula of alkanes is CₙH₂ₙ₊₂

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10
Q

What is a hydrocarbon?

A

A compound containing only hydrogen and carbon

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11
Q

What is a mixture?

A

a substance that contains 2 or more elements that are not chemically bonded together

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12
Q

What does oxidised mean?

A

A substance that has had oxygen added to it and/or has lost electrons

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13
Q

What is a saturated hydrocarbon?

A

A hydrocarbon with only single bonds between its carbon atoms. This means that it contains as many hydrogen atoms as possible in each molecule

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14
Q

What is an unsaturated hydrocarbon?

A

A hydrocarbon whose molecules contain at least 1 carbon-carbon double bond

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15
Q

What does viscosity mean?

A

The resistance of a liquid to flowing or pouring; a liquids “thickness”

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16
Q

What does volatility mean?

A

how readily a substance vaporizes

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17
Q

What is the general formula of an alkane?

A

CₙH₂ₙ₊₂

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18
Q

What are the first 5 alkanes?

A

Methane, Ethane, Propane, Butane, Pentane

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19
Q

What is the molecular formula of Methane?

A

CH₄

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20
Q

What is the molecular formula of Ethane?

A

C₂H₆

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21
Q

What is the molecular formula for Propane?

A

C₃H₈

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22
Q

What is the molecular formula for Butane?

A

C₄H₁₀

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23
Q

What is the molecular formula for Pentane?

A

C₅H₁₂

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24
Q

What is a homologous series?

A

a group of organic compounds with similar chemical properties who share the same general formula.

25
Q

What is complete combustion?

A

When a hydrocarbon burns in the maximum amount of oxygen to form water and carbon dioxide

26
Q

What type of reaction is complete combustion?

A

An oxidation reaction as the hydrocarbons gain oxygen and lose electrons. It is also an exothermic reaction as energy is released to the surroundings during the reaction

27
Q

What is the equation for methane undergoing complete combustion?

A

CH₄(g) + 2O₂(g) -> CO₂(g) + 2H₂O(g)

28
Q

What is the equation for ethane undergoing complete combustion?

A

2C₂H₆(g) + 7O₂(g) -> 4CO₂(g) + 6H₂O(g)

29
Q

What is the equation for propane undergoing complete combustion?

A

C₃H₈(g) + 5O₂(g) -> 3CO₂(g) + 4H₂O(g)

30
Q

What is the equation for butane undergoing complete combustion?

A

2C₄H₁₀(g) + 13O₂(g) -> 8CO₂(g) + 10H₂O(g)

31
Q

What is the equation for pentane undergoing complete combustion?

A

C₅H₁₂(g) + 8O₂ -> 5CO₂ + 6H₂O

32
Q

What is crude oil?

A

a finite resource found in rocks that is a mixture of many different compounds known as hydrocarbons. It is the remains of an ancient biomass. Most of the hydrocarbons in crude oil are alkanes.

33
Q

Explain how fractional distillation works:

A

The crude oil is heated as it enters the fractionating column until it becomes vaporised. The vapor is then passed into the fractionating column. The fractionating column is cooler at the top than at the base. Inside the fractionating column there are many trays with holes to allow gases through. The hydrocarbons rise up the fractionating column, cooling as they rise. Once the hydrocarbon reaches its boiling point, it condenses and forms a liquid, collecting in a fraction on the tray. They are then tapped off and collected. As the hydrocarbons have different boiling points, they condense at different temperatures, and are therefore tapped off at different levels. The smaller the molecule the higher up the column they reach before condensing as they have a lower boiling point. By doing this, fractions of hydrocarbons are separated.

34
Q

Are fractions pure substances or mixtures?

A

A mixture, the fraction boils over a range of temperatures rather than at 1 specific temperature

35
Q

What are the properties of small hydrocarbons?

A
  • Low boiling point
  • High flammability
  • Clean flame
  • Low viscosity
  • High volatility
36
Q

What are the properties of large hydrocarbons?

A
  • High boiling points
  • Low flammability
  • Smoky flame
  • High viscosity
  • Low volatility
37
Q

Which properties of hydrocarbons does fractional distillation depend on?

A

Different boiling points

38
Q

What are the 2 types of cracking?

A
  • Catalytic cracking

* Steam cracking

39
Q

What are the products of cracking?

A

alkanes and alkenes

40
Q

Are alkanes or alkenes more reactive?

A

Alkenes

41
Q

What is the displayed formula of Methane?

A
42
Q

What is the displayed formula of Ethane?

A
43
Q

What is the displayed formula of Propane?

A
44
Q

What is the displayed formula of Butane?

A
45
Q

What is the displayed formula of Pentane?

A
46
Q

Are longer or shorter hydrocarbons more useful as fuels and why?

A

Shorter chain hydrocarbons are more useful as fuels. Longer chain hydrocarbons are more viscous, not very flammable, and burn with a dirty flame - producing a lot of smoke. Whereas, shorter chain hydrocarbons are less viscous, more flammable, and burn with a clean flame - producing little smoke

47
Q

How do you test for water?

A
  • Blue cobalt chloride paper turns pink in contact with water
  • White anhydrous copper sulfate turns blue in contact with water
48
Q

How do you test for carbon dioxide?

A

Limewater turns cloudy when carbon dioxide is present

49
Q

What is incomplete combustion?

A

In a limited supply of oxygen, the fuel may not burn completely, forming carbon monoxide, carbon, and water

50
Q

Why are alkenes more reactive than alkanes?

A

They contain a double bond

51
Q

Why is incomplete combustion worse than complete combustion?

A

Incomplete combustion releases less energy than complete combustion and forms the colourless, odourless, and toxic gas carbon monoxide (it is toxic as your red blood cells pick up the gas and carry it in your blood instead of oxygen)

52
Q

What reactions occur during cracking

A

Thermal decomposition reactions

53
Q

What is the test for alkenes?

A

A positive test for an unsaturated hydrocarbon is that it turns orange bromine water colourless (alkanes do not react with bromine water)

54
Q

What are the uses of crude oil?

A
  • Fuels
  • Polymers
  • Solvents
  • lubricants
  • Detergents
55
Q

Explain how catalytic cracking works:

A

1) The long-chain hydrocarbons are heated until they vaporise
2) The vapour is passed over a hot catalyst
3) The long chain hydrocarbons split apart on the surface of the catalyst to form a shorter alkane and alkenes

56
Q

Explain how steam cracking works:

A

1) The long-chain hydrocarbons are heated until they vaporise
2) They are then mixed with steam and heated to an extremely high temperature
3) The long-chain hydrocarbon splits to form a shorter alkane and alkenes

57
Q

What is a saturated hydrocarbon known as?

A

An alkane

58
Q

What is an unsaturated hydrocarbon known as?

A

An alkene

59
Q

Why are large hydrocarbon molecules often cracked to produce smaller hydrocarbon molecules?

A
  • There is a greater demand for short chain hydrocarbon
  • This is because shorter chain hydrocarbons are more useful as they are more flammable, less viscous, more volatile, burn with a cleaner flame, and have a lower boiling point

GCSE Chemistry (15 decks)

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