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IGCSE edexcel Chemistry > Organic Chemistry > Flashcards

Organic Chemistry Flashcards

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1
Q

What is Crude oil?

A

A non renewable source made up of a mixture of hydrocarbons

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2
Q

What is a hydrocarbon?

A

A molecule made up only of hydrogen and carbon

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3
Q

What is a fraction?

A

A type of hydrocarbon with a specific range of boiling points

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4
Q

What is a homologous group?

A

A group of chemicals with similar characteristics and a trend seen. They have the same general formula.

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5
Q

How does fractional distillation work?

A

The crude oil is put in a very hot furnace, where it vaporises. It is then transferred to the column, with a temperature gradient, where vapour rises up column and the fractions separate. When a fraction reaches its boiling point it reliquifies, so it can be collected for use.

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6
Q

What trends do you see as the molecule size increases?

A
  • boiling point increases, a larger molecule w greater intermolecular forces ∴ more energy needed to break them
  • viscosity increases; liquids w large molecules stickier as inter molecular attractions greater
  • Volatility decreases- evaporates slower at room temp as bigger molecules more attracted to each other
  • Flammability decreases- greater inter molecular forces, so won’t combust as easily
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7
Q

What can we make from crude oil(in order of increasing boiling point)?

A
  • refinery gases
  • petrol
  • naphtha
  • kerosine
  • diesel
  • fuel oil
  • lubricating oil
  • bitumen
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8
Q

What are alkanes?

A
  • what crude oil is mainly made of
  • homologous series
  • general formula CnH2n+2
  • saturated(all single bonds)
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9
Q

What is an isomer?

A

When the molecular formula is the same, but it is arranged in a different way, so the structure is different

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10
Q

Name the first four alkanes

A 
Methane
Ethane
Propane
Butane
Pentane
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11
Q

Describe the reaction of methane with bromine.

What is the chemical equation?

A

In the presence of UV light, methane reacts with bromine to form bromomethane and hydrogen bromide.
CH4 + Br2 => CH3Br + HBr

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12
Q

What are alkenes?

A
  • unsaturated(has a double bond)

* general formula is C2nH2n

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13
Q

What is the test for alkenes?

A

When added to bromine water it turns from orange to colourless.

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14
Q

Why do we need cracking?

A

Fractional distillation makes many more long-chain hydrocarbons than can be used, and fewer short-chain hydrocarbons than we need, so we use cracking.

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15
Q

What does cracking produce?

A

It produces a shorter alkane, and an alkene, from a long chain alkane

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16
Q

What type of reaction is cracking?

A

Thermal decomposition- breaking down molecules by heating them

17
Q

What is the process of cracking?

A
  1. Long chain hydrocarbon is heated to vaporise it
  2. Vapour is passed over a catalyst(alumina) at 600-700°C
  3. The long chain molecules are split apart
18
Q

What is the equation for complete combustion?

A

Alkane + oxygen => carbon dioxide + water (+energy)

19
Q

Why is complete combustion good?

A
  • releases lots of energy
  • only produces two, harmless waste products
  • clean, blue flame
20
Q

What is the equation for incomplete combustion?

A

Alkane + oxygen => carbon + carbon monoxide + CO2 + H2O (+ energy)

21
Q

Why is incomplete combustion bad?

A
  • less energy is produced
  • smoky yellow flame
  • carbon monoxide is v toxic, as decreases body’s ability to transport oxygen
  • carbon produces sooty marks
22
Q

How do you avoid incomplete combustion?

A

Make sure there is a good supply of oxygen when burning fuel

23
Q

How do car engines contribute to acid rain?

A
  • the temps can be high enough to allow nitrogen and oxygen from the air to react and form nitrous oxides
  • this leads to acid rain, as well as SO2
24
Q

What is a polymer?

A

Long chain molecules made from lots of smaller molecules joined together

25
Q

What is a monomer?

A

Small molecules that join together to make polymers

26
Q

What is polymerisation?

A

Formation of long chain molecules from lots of smaller molecules joined together

27
Q

What is addition polymerisation?

A
  • made of one type of monomer that repeats itself
  • must be made of alkenes, as the double C=C bond changes to a single bond
  • long chains of hydrocarbons are formed
28
Q

What are the properties and uses of polyethene?

A
  • low density, flexible; plastic bags

* high density, strong and rigid; plastic bottles

29
Q

What are the properties and uses of Poly Propene?

A

Stronger than polyethene. Used for ropes and crates

30
Q

What are the uses and properties of polychloroethene?

A
  • strong and rigid- window frames, drain pipes

* electrical insulator- electrical insulation

31
Q

What is condensation polymerisation?

A
  • two different monomer

* form small molecule, normally water, when joined together

32
Q

What are alcohols?

A
  • homologous series
  • -OH functional group
  • C2 H2n+1 OH
  • can make isomers
33
Q

Why are polymers bad for the environment?

A
  • they aren’t broken down by bacteria
  • they only got smaller, not simpler
  • when incinerated, it must be very efficient otherwise it produces toxic substances e.g. Hydrogen cyandide
34
Q

How does fermentation work?

A
  • zymase left with starch or sugar for several days in warm conditions
  • starch/sugar turns into fructose and glucose
  • these then turn into ethanol and carbon dioxide
  • this is not pure, but can be further purified by fractional distillation
35
Q

How does hydration work?

A
  • high temperatures and pressures needed (250-350°C and 65 atm)
  • ethene passed over catalyst(phosphoric acid) constantly
  • this produces ethanol
36
Q

How do you make ethanol from crude oil?

A
  • extract the crude oil
  • use fractional distillation to get alkanes of similar length
  • crack long chain alkanes to make an alkene
  • hydrate the alkenes to make alcohol
37
Q

How do you dehydrate ethanol?

A
  • pass it over a catalyst(hot aluminium oxide)
  • this removes the OH group and an extra H
  • the ethanol is turned into ethene

IGCSE edexcel Chemistry (12 decks)

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