Organic Chemistry 4.1-4.28
No description yet. This curated deck is ready for daily study.
Card preview (24)
4.1 What is a hydrocarbon?
A compound of hydrogen and carbon only
4.2 How do you represent molecules using molecular formulae
Actual number of each type of atom present e.g. C2H4 = ethene
4.2 How do you represent molecules using empirical formulae?
Simplest whole number ratio e.g. C2H6 = CH3
4.2 How do you represent molecules using general formulae
General formula for the homologous series e.g. CnH2n
4.7 What is crude oil
A mixture of hydrocarbons
4.2 How do you represent molecules using a) structural formulae b) displayed formulae
a) How the atoms are joined together b) Show all bonds in the molecule as lines (covalent bond)
4.3 What is a homologous series?
Group of compounds with - same general formula, trends in their physical properties, similar chemical properties, trends in their physical properties, each successive member differs by CH2, same functional group
4.3 What is a functional group
An atom or group of atoms that determines the chemical properties of the compound
4.20 What does saturated mean
Contains single bonds only
4.19 What is the general formula of alkanes
CnH2n+2
• 4 What is the number of carbon atom(s) in a) propane b) ethane c) methane d) butane
3, 2, 1, 4
4.6 Reaction of alkanes with bromine with ultraviolet light
A substitution reaction occurs as a hydrogen atom on the alkane has been replaced by a bromine atom methane + bromine (red/brown) -> bromomethane + hydrogen bromide (colourless) CH4 + Br2 -> CH3Br + HBr More examples: C3H8 + Br2 -> C3H7Br (Bromopropane) + HBr
4.6 Combustion of alkanes
Complete combustion: alkane + oxygen -> carbon dioxide + water e.g. CH4 + 2O2 -> CO2 +2H20
4.6 and 4.12 Combustion of alkanes continued
Incomplete combustion occurs with an insufficient supply of oxygen alkane + oxygen -> carbon monoxide + water alkane + oxygen -> carbon + water
4.3 What is structural isomerism
Structural isomers are molecules with the same molecular formula, but different structural formulae
4.8 How does fractional distillation separate crude oil into fractions
• Crude oil is heated and enters the fractioning column • The column is hotter at the bottom and gets cooler as you go up • Large molecules with high boiling points condense near the bottom • Small molecules with low boiling points remain as gases and leave at the tap
4.9 What are the uses and names of the main fractions obtained from crude oil (6)
a) Refinery gases - liquefied petroleum gas for domestic cooking b) Gasoline - fuel in cars c) Kerosene - fuel for jet aircrafts, domestic heating oil and ‘paraffin’ for small heaters and lamps d) Diesel- fuel for buses and lorries e) Fuel oil - fuel for ships f) Bitumen - road surface tar
4.13 Why is carbon monoxide poisonous
Carbon monoxide is toxic because it reduces the capacity of blood to transport oxygen around the body
4.11 What is a fuel
A substance that when burned releases heat energy
4.10 What are the trends in the main fractions of a) colour b) boiling point and c) viscosity
Molecules get larger as you go down Colour lighter at top and darker at the bottom Boiling point lower at the top and higher at the bottom Viscosity lower at the top (runny) and higher at the bottom (thicker)
4.14 Why in car engines can nitrogen and oxygen react
The temperature reached is high enough to allow nitrogen and oxygen from air to react, forming oxides of nitrogen N2 (g) + O2 (g) ->2NO (g) nitrogen oxide N2 (g) + 2O2 (g) -> 2NO2 (g) nitrogen dioxide
4.15 How does sulphur dioxide form via combustion
Fossil fuels contain sulfur as an impurity and when they burn, the sulfur is also oxidised to form: sulfur dioxide = S(s) + O2 (g) -> SO2 (g) and in water forms an acidic solution sulfurous acid = SO2 (g) + H20 (l) -> H2SO3 (aq) + oxygen = 2H2SO3 + O2 -> 2H2SO4 (sulfuric acid)
4.16 How does sulfur dioxide and oxides of nitrogen contribute to acid rain
They dissolve in water to form acidic solutions
4.18 Why is cracking necessary
The supply of short chain hydrocarbons from crude oil is not enough to meet demand Supply of long chain hydrocarbons is larger than demand