Organic Chemistry Flashcards
1
Q
What atoms do hydrocarbons contain?
A
- hydrogen
- carbon
2
Q
Alkanes
A
- simplest type of hydrocarbon
- C(n)H(2n+2)
- homologous series
- saturated compounds (each carbon atom forms four single covalent bonds)
3
Q
Homologous series
A
Group of organic compounds that react in a similar way
4
Q
First four alkanes in order
A
Methane
Ethane
Propane
Butane
5
Q
Properties of short hydrocarbons
A
- lower viscosity
- more volatile (turns into gas at a lower temperature)
- lower boiling point
- more volatile
6
Q
Properties of large hydrocarbons
A
- higher viscosity
- less volatile (turns into a gas at a higher temperature)
- higher boiling point
- less flammable
7
Q
Complete combustion of any hydrocarbon (word equation)
A
Hydrocarbon + oxygen => carbon dioxide + water
8
Q
Combustion of hydrocarbons
A
- carbon and hydrogen are both oxidised (gain of oxygen)
- used as fuels; large amounts of energy from burning
- waste products are carbon dioxide and water
9
Q
How is crude oil made?
A
- fossil fuel
- formed from remains of plants and animals (mainly plankton)
- died millions of years ago and buried under mud
- high temperatures and pressures turned the remains to crude oil
- finite resources
10
Q
Separation of crude oil
A
- mixture of many hydrocarbons, mainly alkanes
- requires fractional distillation to separate
11
Q
Fractional distillation of crude oil process
A
- heated until mostly gas; enter fractionating column
- temperature gradient - cooler at top
- longer hydrocarbons have high boiling points, so they condense lower down the column
- shorter hydrocarbons have low boiling points, so they rise to the top of the column before they condense
- crude oil separated into different fractions
12
Q
Main fractions of crude oil (shortest to longest hydrocarbons)
A
- LPG (liquefied petroleum gas)
- petrol
- kerosene
- diesel oil
- heavy fuel oil
13
Q
Uses of crude oil
A
- fuel for most modern transport
- petrochemical industry (plastics, solvents, lubricants, detergents, etc.)
14
Q
Why do we crack hydrocarbons?
A
- short-chain hydrocarbons are in high demand
- long-chain hydrocarbons are less useful
- turn longer molecules into smaller ones
- also produces alkenes
15
Q
Catalytic cracking
A
- thermal decomposition reaction
- heat long-chain hydrocarbons to vaporise them
- vapour passed over hot powdered aluminium oxide catalyst
- long-chain molecules split apart on specks of catalyst
16
Q
Steam cracking
A
- heat hydrocarbons to vaporise them
- mix them with steam
- heat to a very high temperature
17
Q
Alkenes
A
- hydrocarbons with a double bond between two C atoms in their chain
- C=C bond means they have 2 less hydrogens; unsaturated
- C=C can open up to make a single bond; makes alkenes reactive
- C(n)H(2n)
18
Q
First four alkenes
A
Ethene
Propene
Butene
Pentene
19
Q
Combustion of alkenes
A
- combust completely in abundance of oxygen
- produces carbon dioxide and water
- burn in air; incomplete combustion
- carbon dioxide, water and carbon monoxide
- smoky yellow flame; less energy released
20
Q
Standard equation for incomplete combustion of alkenes
A
Alkene + oxygen => carbon + carbon monoxide + carbon dioxide + water
21
Q
Functional Group
A
- group of atoms in a molecule
- determine how that molecule typically reacts
22
Q
Addition Reactions of alkenes
A
- C=C functional group
- predict products of reaction based on how alkenes react in general
- double bond opens up to leave a single bond, and a new atom is added to each carbon
23
Q
Alkenes reactions with halogens
A
- react in addition reactions with halogens
- forms saturated molecules with C=C carbons each bonding to a halogen atom
- e.g. bromine and ethene react to form dibromoethane
24
Q
Test for alkenes
A
- orange bromine water added to a saturated compound; no reaction will happen, no colour change
- bromine water added to an alkene
- bromine will add across the double bond, making a colourless dibromo-compound
- bromine water is decolourised
25
Reaction of alkenes with steam
- water added across the double bond and an alcohol is formed
- ethanol made by mixing ethene with steam and then passing over a catalyst
- purified by fractional distillation
26
Polymers
- long molecules
- formed when lots of small molecules called monomers join together
- plastics made up of polymers; usually carbon-based and polymers are alkenes
27
Polymerisation
- many monomers joining together into a polymer
| - usually needs high pressure and a catalyst
28
Addition Polymerisation
- monomers have a double covalent bond
- lots of unsaturated monomer molecules open up double bonds and join to form polymer chains
- only product is the polymer - exactly same type/number of atoms as the monomers that formed it
29
Condensation Polymerisation
- monomers which contain different functional groups
- monomers react and form bonds, making polymer chains
- each new bond that forms, a small molecule (e.g. water) is lost - hence the name condensation polymerisation
- simplest types contain two different types of monomer, each with two of the same functional groups
30
What two elements do hydrocarbons contain?
Hydrogen and Carbon
31
What is the hottest part of a fractional distillation column?
It is hotter towards the bottom
32
Name two methods of cracking
Steam cracking
| Catalytic Cracking
33
Give a product of cracking that is used for making plastics
Alkenea
34
General formula for an alkene
C(n) H(2n)
35
General formula for an alkane
C(n)H(2n+2)
36
Give a word equation for the complete combustion of butane
Butane + oxygen => carbon dioxide + water
37
What is used to test for alkenes?
Bromine water
38
What type of compounds are used as the monomers to make addition polymers
Alkenes
