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Chemistry GCSE 2020 > C7: Organic chemistry > Flashcards

C7: Organic chemistry Flashcards

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1
Q

What makes something “organic” in the chemical sense?

A

It contains carbon.

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2
Q

What is crude oil?

A
  • A finite resource found in rocks: the remains of an ancient biomass, consisting mainly of plankton that was buried in mud.
  • Is a mixture of a large number of compounds, mostly hydrocarbons.
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3
Q

What are hydrocarbons?

A

Molecules made only of hydrogen and carbon.

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4
Q

Most of the hydrocarbons in crude oil are what?

A

Alkanes.

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5
Q

What is the general formula for alkanes?

A

CnH2n + 2

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6
Q

What is meant by the term “homologous series”?

A

A series of compounds with the same functional group and similar chemical properties.

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7
Q

What are the names of the first four members of the alkanes?

A
  • Methane
  • Ethane
  • Propane
  • Butane
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8
Q

What is fractional distillation and what is its purpose?

A
  • The process by which hydrocarbons in crude oil are separated into fractions.
  • The fractions can be processed to produce fuels and feedstock for the petrochemical industry.
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9
Q

Explain how the process of fractional distillation works.

A
  • Crude oil is heated until the hydrocarbons evaporate.
  • The hydrocarbons rise through the column.
  • The hydrocarbons condense and different fractions are extracted in different parts of the column.
  • Longer hydrocarbons condense in the lower parts of the column; shorter ones in the upper parts.
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10
Q

Name 5 fuels produced by fractional distillation from crude oil.

A
  • Petrol
  • Diesel oil
  • Kerosene
  • Heavy fuel oil
  • Liquefied petroleum gases
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11
Q

Name 4 useful materials produced by the petrochemical industry.

A
  • Solvents
  • Lubricants
  • Polymers
  • Detergents
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12
Q

Why is there such a vast array of natural and synthetic carbon compounds?

A

Carbon atoms have the ability to form families of similar compounds (homologous series).

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13
Q

What 3 properties of hydrocarbons depend on the size of molecules?

A
  • volatility (boiling points)
  • viscosity (runniness)
  • flammability
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14
Q

For hydrocarbons, how does boiling point change with increasing molecular size?

A
  • Longer hydrocarbon chains have more cumulative intermolecular forces which require more energy to overcome
  • So their boiling points are higher
  • Shorter chains have less cumulative intermolecular forces, so it takes less energy to separate molecules
  • So they are more volatile
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15
Q

For hydrocarbons, how does viscosity change with increasing molecular size?

A
  • Longer hydrocarbon chains have more cumulative intermolecular forces which require more energy to overcome
  • So they are more viscous
  • Shorter chains have less cumulative intermolecular forces, so it takes less energy to separate molecules
  • So they are less viscous
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16
Q

For hydrocarbons, how does flammability change with increasing molecular size?

A
  • Longer hydrocarbon chains have more cumulative intermolecular forces which require more energy to overcome
  • So they are less flammable
  • Shorter chains have less cumulative intermolecular forces, so it takes less energy to separate molecules
  • So they are more flammable
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17
Q

What happens during the combustion of hydrocarbons?

A
  • The carbon and hydrogen in the fuels are oxidised
  • Energy is released
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18
Q

Write the general equation for the complete combustion of a hydrocarbon.

A

Hydrocarbon + oxygen → carbon dioxide + water

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19
Q

What are alkenes?

A

Hydrocarbons with the functional group C=C (with a double carbon-carbon bond).

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20
Q

What is cracking and what is its purpose?

A
  • The process by which long-chain hydrocarbons are broken down to produce smaller, more useful molecules by thermal decomposition
  • The products of cracking are alkanes and alkenes
  • Some of the products of cracking - the small ones - are used for fuels because they are flammable
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21
Q

How are alkenes (produced by cracking) useful?

A
  • Used to produce polymers
  • Used as starting materials for the production of many chemicals
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22
Q

Name 2 types of cracking.

A
  • Catalytic cracking
  • Steam cracking
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23
Q

Describe the conditions used for catalytic cracking.

A
  • It is a thermal decomposition reaction
  • Long-chain hydrocarbons are heated and vaporised
  • Vapour is passed over a powdered aluminium oxide catalyst
  • The molecules split apart on the surface of the specks of catalyst
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24
Q

Describe the conditions used for steam cracking.

A
  • It is a thermal decomposition reaction
  • Long-chain hydrocarbons are heated and vaporised
  • Vapour is mixed with steam and heated to a very high temperature
  • The molecules split apart
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25
Q

Which are more reactive: alkanes or alkenes?

A

Alkenes.

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26
Q

How would you test for alkenes?

A
  • Add bromine water, which is bright orange
  • Positive result: solution goes colourless
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27
Q

What is the general formula for alkenes?

A

CnH2n

28
Q

Which out of alkanes and alkenes are saturated and unsaturated? Explain why.

A
  • Alkanes are saturated because all C-C bonds are single.
  • Alkenes are unsaturated because they contain a double C-C bond (C=C).
29
Q

What are the names of the first four alkenes?

A
  • Ethene
  • Propene
  • Butene
  • Pentene
30
Q

How do alkenes combust?

A
  • Alkenes can react completely with oxygen in the same way as all hydrocarbons.
  • But they tend to react incompletely, burning with a smoky flame.
31
Q

How do alkenes react with hydrogen?

A

Addition reactions:

  • Hydrogen is added across the C=C bond
  • The C=C bond then becomes a C-C bond
  • Each of the carbons in that bond is bonded to one hydrogen atom
  • The molecule becomes saturated
32
Q

How do alkenes react with the halogens?

A

Addition reactions:

  • The halogen is added across the C=C bond
  • The C=C bond then becomes a C-C bond
  • Each of the carbons in that bond is bonded to one halogen atom
  • The molecule becomes saturated
33
Q

How do alkenes react with water?

A

Addition reactions:

  • When alkenes are reacted with steam, alcohols are formed
  • Water is added across the C=C bond
  • The C=C bond then becomes a C-C bond
  • Each of the carbons in that bond is bonded to one hydrogen atom. One carbon also bonds like this: C-O-H
  • The molecule becomes saturated
34
Q

What is the functional group of alcohols?

A

-O-H

35
Q

What is the general formula of alcohols?

A

CnH2n+1OH

36
Q

What are the names of the first four alcohols?

A
  • Methanol
  • Ethanol
  • Propanol
  • Butanol
37
Q

Describe what happens when one of the first 4 alcohols burns in air.

A
  • They are flammable so combust completely in air
  • This produces carbon dioxide and water
38
Q

Describe what happens when one of the first four alcohols is added to water.

A

They dissolve, forming neutral pH solutions.

39
Q

Describe what happens when one of the first four alcohols reacts with an oxidising agent.

A

They react with oxygen to produce carboxylic acids.

40
Q

Describe what happens when one of the first four alcohols reacts with sodium.

A
  • This produces sodium []oxide and hydrogen gas.
  • Ethanol reacts to produce sodium ethoxide and hydrogen gas.
41
Q

What happens when sugar solutions are fermented using yeast? What should the conditions be for fermentation?

A
  • Happens fastest at 37°C, in a slightly acidic solution and under anaerobic conditions
  • An aqueous solution of ethanol is produced (an enzyme in yeast converts the sugar to ethanol)
42
Q

Name 2 uses of alcohols.

A
  • Solvents
  • Fuels
43
Q

Why are alcohols used in solvents?

A

They can dissolve most things that water can, but also things that water cannot (hydrocarbons, oils, fats).

44
Q

How are alcohols used as fuels?

A

The first 4 are used as fuels, because they are flammable.

45
Q

What is the functional group of carboxylic acids?

A

-C-O-O-H

46
Q

What are the names of the first 4 carboxylic acids?

A
  • Methanoic acid
  • Ethanoic acid
  • Propanoic acid
  • Butanoic acid
47
Q

What is the general formula of carboxylic acids?

A

CnH2n+1COOH

48
Q

Describe what happens when any of the first 4 carboxylic acids reacts with carbonates.

A

They react to produce a salt (ending in “anoate”), water and carbon dioxide.

49
Q

ethanoic acid + sodium carbonate →

A

sodium ethanoate + water + carbon dioxide

50
Q

Describe what happens when one of the first 4 carboxylic acids are placed in water.

A

They dissolve, then ionise (but not completely), resulting in a weakly acidic solution.

51
Q

Why are carboxylic acids weak?

A
  • When placed in water, they dissolve, then ionise, resulting in an acidic solution
  • But they don’t ionise completely (not all acid molecules release H+ ions)
  • So they only form weak acidic solutions
  • This means they have a higher pH than that of solutions, of the same concentration, of strong acids
52
Q

Describe what happens when alcohols react with carboxylic acids.

A

They react to produce esters.

53
Q

What is the functional group of esters?

A

-C-O-O

54
Q

ethanoic acid + ethanol →

A

ethyl ethanoate + water

55
Q

Name 2 types of polymerisation.

A
  • Addition polymerisation
  • Condensation polymerisation
56
Q

What happens during addition polymerisation?

A

Many small molecules (monomers: alkenes) join together to form very large molecules (polymers).

57
Q

Draw a diagrame to represent poly(ethene).

A
58
Q

What happens during condensation polymerisation?

A

Monomers with 2 different functional groups join together, usually losing small molecules such as water. The polymers formed contain 2 monomer types.

59
Q

Name 5 naturally occuring polymers.

A
  • Amino acids
  • Proteins
  • DNA
  • Starch
  • Cellulose
60
Q

How do amino acids polymerise?

A
  • Amino acids have 2 different functional groups within a molecule
  • So they react by condensation polymerisation, producing polypeptides
  • Different amino acids are combined in chains to produce proteins, which are also polymers
61
Q

What is DNA?

A

DNA (deoxyribonucleic acid) is a large molecule, essential for life, which encodes genetic instructions for the development and function of living organisms and viruses.

62
Q

DNA is a polymer. Describe its structure.

A

Most DNA molecules are two polymer chains, made from four different monomers called nucleotides, in the form of a double helix.

63
Q

Name the monomer which the polymers proteins are made from.

A

Amino acids.

64
Q

Name the monomer which the polymer starch is made from.

A

Glucose.

65
Q

Name the monomer which the polymer cellulose is made from.

A

Glucose.

Chemistry GCSE 2020 (10 decks)

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