Organic Chemistry Flashcards
What is covalent bonding?
The strong electrostatic force of attraction between the nuclei of bonding atoms and shared common electrons
Does covalent binding only occur in metals or non-metals?
Only non-metals
What shell of electrons do you draw when drawing dot-and-cross diagrams?
Only the outer shell
What is a homologous series?
A series of molecules in which:
- all have the same general formula
- all share similar chemical properties (e.g boiling point)
- all follow trends in physical properties (e.g colour and viscosity)
What is crude oil?
A mixture of hydrocarbons
What is a mixture?
Two or more substances that aren’t chemically bonded together
What is a hydrocarbon?
A compound consisting of only hydrogen and carbon
Describe the process of the fractional distillation of crude oil
- Crude oil is heated and evaporates into a gas
- Vapour passes into the fractionating column, in which the temperature decreases as you travel up it
- Fractions collect where the temperature in the fractionating column is equal to or below their boiling point and they condense
- Fractions are then piped out of the fractionating column as liquids (or gases if its refinery gas)
What are the six gases in order of which they come out of the fractionating column?
Bitumen, fuel oil, diesel, kerosene, gasoline, refinery gas
What is bitumen used for?
Tar
What is fuel oil used for?
Fuel for ships
What is diesel used for?
Fuel for cars/lorries/trains
What is kerosene used for?
Fuel for planes
What is gasoline used for?
Fuel for cars
What is refinery gas used for?
Fuel for household cooking and heating
What is the trend in fractions in terms of size of molecules?
Size of molecule decreases as you go up the fractionating column
What is the trend in fractions in terms of boiling point?
Boiling point decreases as you go up the fractionating column
What is the trend in fractions in terms of viscosity?
Viscosity of fraction decreases as you go up the fractionating column
What is the trend in fractions in terms of colour?
Colour of fraction gets lighter as you go up the fractionating column
What is a fuel?
A fuel is a substance that, when burned, releases heat energy
Complete combustion
When a substance burns in sufficient oxygen
Incomplete combustion
When a substance burns in insufficient oxygen
Word equation for the complete combustion of alkanes
Alkane + oxygen => carbon dioxide + water
Word equations for the incomplete combustion of hydrocarbons
Hydrocarbon + oxygen => carbon + water OR hydrocarbon + oxygen => carbon monoxide + water
Why is carbon monoxide poisonous?
When carbon monoxide produced from incomplete combustion is inhaled into the lungs, the haemoglobin binds to it in preference to oxygen; it irreversibly binds to the haemoglobin producing carboxyhemoglobin. This therefore reduces the blood’s capacity to transport oxygen around the body
How does burning fossil fuels lead to the production of sulphuric acid to cause acid rain?
- fossil fuels contain sulfur as an impurity
- when fossil fuels are burned, the oxygen in the air reacts with the sulphur to produce sulfur dioxide gas
- when the sulfur dioxide passes into the atmosphere,it dissolves into rainwater and makes it become more acidic
- this causes acid rain
How do car engines produce nitrogen oxides and lead to acid rain?
- nitrogen is an inert element that is gas at room temp.
- it makes up 78% of the air around us
- however in car engines, temperatures reach enough for the nitrogen to react with oxygen in the air and produce nitrogen oxides
- these oxides of nitrogen are also acidic, which dissolve into rainwater and make it more acidic and cause acid rain
What is cracking?
A process in which long-chain alkanes are converted into short chain alkanes and Alkenes
Why is cracking necessary, in terms of supply and demand?
- the supply of long-chain alkanes is higher than demand, however the supply of alkenes and short chain alkanes is lower than demand
- therefore , cracking is needed to satisfy supply and demand for shorter chain alkanes and alkenes
Explain how catalytic cracking works
- long chain alkanes are evaporated to gas form
- then they are passed over a hot catalyst (either silica or alumina) at 600-700ºC
- as a result of thermal decomposition, the long-chain alkanes break down to form short chain alkanes and alkenes are produced such as petrol