Paper 2: Fuels And Atmospheric Science Flashcards
What are hydrocarbons
Compounds that contain hydrogen and carbon atoms only
What is crude oil?
- A complex mixture of hydrocarbons.
- Contains molecules with rings or chains of carbon
atoms. - An important source of useful substances like fuels
and feedstocks for the petrochemical industry. - A finite resource.
How can crude oil be separated?
Fractional distillation
How does the process of fractional distillation work to separate crude oil?
- Crude oil is vaporised before it enters a fractionating column.
- The fractionating column is hotter at the bottom than at the top.
- The vapours rise up and condense at different fractions depending on their boiling points.
- Hydrocarbons with low boiling points will be tapped off the top of the column and hydrocarbons with high boiling points will be tapped off the bottom of the column.
Name the crude oil fractions and usages
How do hydrocarbons at each fraction differ?
Boiling points
Ease of ignition
Viscosity
The number of hydrogen and carbon atoms their molecules have
Where in the fractionating column do hydrocarbons with highest viscosity condense?
Viscosity is how thick and sticky a substance is. (How easily it flows)
The hydrocarbons with the highest viscosity (like bitumen) are collected at the bottom of the fractionating column.
What are the properties of hydrocarbons that are tapped from the top of the fractionating column, like petrol and gases
Low boiling point.
- Highly volatile.
- Easily ignited.
- Shorter carbon chains (small molecules).
What is a homologous series?
Series of compounds which: - Have the same general formula. - Have similar chemical properties. - Differ by CH2 in molecular formula form neighbouring molecules. - Slight variation in physical propertie
Products from crude oil mostly belong to which homologous series?
Alkane homologous series.
What are the only products when a hydrocarbon fuel undergoes complete combustion?
Water (H2O) and carbon dioxide (CO2)
True or false?
Energy is given out when a fuel undergoes complete combustion
True
The reaction is exothermic
When does incomplete combustion occur? What is required to ensure complete combustion occurs?
Incomplete combustion occurs when there is an insufficient supply of oxygen.
To ensure complete combustion occurs, the reaction should be carried out with excess oxygen
What are the products of incomplete combustion?
Carbon particulates - soot (C).
Carbon monoxide (CO).
Water (H2O).
What are the problems with carbon monoxide?
Carbon monoxide is a toxic gas.
It is colourless and odourless and if breathed in can cause death by preventing the red blood cells from carrying oxygen around the body.
What are the problems with incomplete combustion?
Produces carbon monoxide which is toxic and can be fatal if breathed in.
- Produces carbon particulates (soot) which cause global dimming and respiratory problems.
Why is sulfur dioxide sometimes produced when burning hydrocarbon fuels?
Some hydrocarbon fuels contain sulfur impurities. When the fuel is burned, the sulfur reacts with oxygen to form sulfur dioxide.
How is acid rain produced?
Sulfur dioxide (produced when combusting impure hydrocarbon fuels) evaporates into the air. It reacts with water in the clouds to form sulfuric acid. This is ‘acid rain”
What problems can acid rain cause?
- Corrodes buildings and statues made of limestone.
- Kills/damages the vegetation.
- Lowers the pH of large bodies of water,
killing the wildlife.
How are oxides of nitrogen produced from car engines?
Car engines are “internal combustion” engines - fuel is mixed with air and ignited inside the engine. This causes temperatures high enough for nitrogen and oxygen in the air inside the engine to react together. Producing various oxides of nitrogen, NOx
What problems are associated with oxides of nitrogen?
- Pollutants.
- Produce acid rain with similar effects
as SO2. - Cause respiratory problems.
What are the advantages of using hydrogen as a fuel in cars?
- It releases more energy per kg compared to most other fuels.
- Water is the only product so no pollutants.
- Renewable source as hydrogen can be
extracted from water
What are the disadvantages of using hydrogen as a fuel in cars?
- It is expensive to produce and a lot of energy is required for the electrolysis of water to acquire the hydrogen.
- Difficult and dangerous to store hydrogen because it is very volatile and easily ignites.
Name the non-renewable fossil fuel found in natural gas
Methane
