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OCR 21st century Chemistry (GCSE) > C3.3 Crude oil > Flashcards

C3.3 Crude oil Flashcards

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1
Q

What is crude oil?

A

A mixture of hydrocarbons that can be separated by fractional distillation

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2
Q

What is a hydrocarbon?

A

A compound consisting of only carbon and hydrogen

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3
Q

Name 2 groups of hydrocarbons

A
  • Alkanes

- Alkenes

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4
Q

Formula for alkanes

A

Cn H2n+2

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5
Q

Name first 4 alkanes

A
  • methane CH4
  • ethane C2H6
  • propane C3H8
  • butane C4H10
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6
Q

Properties of alkanes

A
  • All alkanes contain strong covalent bonds between carbon and hydrogen atoms
  • They are the only saturated hydrocarbons
AS THE CARBON CHAIN INCREASES:
.BP and MP increases
.viscosity(thickness) increases
.less volatile
.less flammable
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7
Q

Explanation on BP and MP on alkanes

A

As the carbon chain increases it means that there are more hydrogen and carbon atoms so there are stronger intermolecular forces so more energy is needed to break those bonds/forces

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8
Q

Explain fractional distillation of crude oil

A
  1. Crude oil is heated until most of it has evaporated and turned into a gas
  2. The evaporated crude oil enters the fractionating column
  3. The column is heated from the bottom so there is a temperature gradient (hottest at the bottom,coolest at the top)
  4. Long chain hydrocarbons have high BPs so they condense at the bottom and short hydrocarbons have low MPs so they condense at the top
  5. When the hydrocarbons reach a height in the column where the temperature is equal to its boiling point, it condenses to form a liquid
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9
Q

What is empirical formula?

A

The simplified whole number ratio of the number of atoms in a chemical formula of a compound

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10
Q

properties of covalent compounds

A
  • low MP and BPs
  • Cannot conduct electricity
  • weaker intermolecular forces of attraction between atoms
  • Atoms share electrons rather than transfer them
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11
Q

Advantages of molecular formula

A
  • Tells you how many atoms of each element

- Used in equations

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12
Q

Disadvantages of molecular formula

A
  • Doesn’t tell you the size of the atom

- Doesn’t tell you the structure or shape of the atom

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13
Q

Advantages of empirical formula

A

-Tells you the ratio of atoms in a formula as a whole number

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14
Q

Disadvantages of empirical formula

A

-Doesn’t always tell you the exact ratio as it may be rounded

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15
Q

Advantages of structural formula

A
  • Shows arrangement of bonds in 2D

- Tells you how many electrons are transferred and how many bonds there are

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16
Q

Disadvantages of structural formula

A
  • Doesn’t show the atoms size
  • Doesn’t show the bond angles
  • Not useful for equations
17
Q

Advantages of ball and stick model

A
  • Shows shape of the molecule in 3D

- Show bond angles

18
Q

Disadvantages of ball and stick model

A
  • Doesn’t show the actual atoms size

- Sizes of the atoms are not 100% accurate

19
Q

What is cracking?

A

When a large hydrocarbon molecule is heated in the presence of a catalyst to break it down into smaller hydrocarbons

20
Q

Why is cracking used?

A

Cracking is used because shorter chain hydrocarbons are in higher demand than long chain ones so in order to meet the demand cracking is used

21
Q

What is thermal cracking?

A

A form of cracking using high temperature and pressure

22
Q

What is catalytic cracking?

A

A form of cracking which uses low temperature and pressure to crack the hydrocarbons

  • It is cheaper
  • Used in industries
23
Q

What is formed as a result of cracking?

A

Long chain alkane ——-> shorter chain alkane + alkene

24
Q

Why do oil companies use cracking?

A
  • Meet demand
  • Produces more fuel
  • Produces alkenes which can be used as plastic or feedstock for other compounds
25
Q

Formula for alkenes

A

Cn H2n

26
Q

Name first 4 alkenes

A
  • ethene C2H4
  • propene C3H6
  • butene C4H8
  • pentene C5H10
27
Q

Properties of alkenes

A
  • Unsaturated
  • Always have at least one double bound between carbon atoms
  • Insoluble in water
  • BP and MP increase as carbon chain increases
  • More flammable than alkanes
28
Q

How do you test for alkenes?

A

Use bromine water:

  • when mixed with an alkene it will go colorless
  • when mixed with an alkane it stays the same
29
Q

Name the 4 functional groups

A

C=C alkene
-OH alcohol
COOH carboxylic acid
COO ester

30
Q

Formula for complete combustion of alkenes, carboxylic acids, alkanes and alcohols

A

carboxylic acids/alcohol/alkene/alkane + oxygen —> carbon dioxide + water

31
Q

Formula for alcohols

A

Cn H2n+1 OH

32
Q

Name first 4 alcohols

A
  • methanol CH3OH
  • ethanol C2H5OH
  • propanol C3H7OH
  • butanol C4H9OH
33
Q

Properties and uses of alcohols

A
  • Highly flammable
  • Used as industrial solvents that are miscible (form a mixture) in water
  • Form solutions with water that have a neutral pH
  • Can be oxidised to form a carboxylic acid
34
Q

Formula for carboxylic acids

A

Cn H2n+1 COOH

35
Q

Name first 4 carboxylic acids

A
  • methanoic acid HCOOH
  • ethanoic acid CH3COOH
  • propanoic acid C2H5COOH
  • butanoic acid C3H7COOH
36
Q

Properties and uses of carboxylic acids

A
  • Weak acids that can dissolve in water
  • When dissolved they partially ionise to release H+ ions and form acidic solutions
  • used in personal care products such as soap, vinegar, aspirin etc.

OCR 21st century Chemistry (GCSE) (3 decks)

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