Non Renewables - Seneca Flashcards
Why is crude oil a mixture
Crude oil is a mixture of lots of different compounds that are not chemically combined. Most of the compounds in crude oil are hydrocarbons.
What property of hydrocarbons can change their properties ?
Hydrocarbons differ in their size, which can change the properties of the hydrocarbon.
What are most compounds in crude oil ?
Most compounds are hydrocarbons
Where is crude oil found ?
Crude oil is found in rocks and is used to produce fuels and other important chemicals.
Crude oil is made from the fossilised remnants of ancient plankton.
Short and long chain hydrocarbons
Hydrocarbons with few carbon atoms are called ‘short-chain hydrocarbons’.
Long-chain hydrocarbons
Hydrocarbons with lots of carbon atoms are called ‘long-chain’ hydrocarbons
What are fractions of fractional distillation ?
Fractional distillation is the process of separating crude oil into groups of hydrocarbons with similar numbers of carbon atoms. We call these groups of hydrocarbons “fractions”.
Collection of fractions from fractional distillation
Collection
The fractions are collected. They are then processed to create end products:Fuels (e.g. petrol, diesel) are a common end product.The petrochemical industry can use some fractions as feedstock (material used in an industrial process) to make products such as solvents, detergents, lubricants etc.
Uses of the fractions of crude oil
Bitumen
Surfacing roads and roofs
Fuel oil
Fuel for ships and power stations
Diesel Oil
Fuel for some cars and trains
Kerosene
Fuel for aircrafts
Gases
Domestic heating and cooking
Petrol
Fuel for cars
Where is the temperature highest in a fractional distillation column ?
Fractional distillation works because different sizes of hydrocarbons have different boiling points. At the bottom of the column, where the temperature is highest, long-chain hydrocarbons condense and are collected as liquids.
Properties of a homologous series
Physical and chemical properties
The members of the homologous series have similar chemical properties, but the physical properties can change.
For example, as the carbon chain becomes longer, the boiling point increases.
Molecular formulas
The molecular formulas of neighbouring compounds differ by a CH2unit.
What Is a homologous series ?
The homologous series is a series of compounds with the same general formula.
Three important properties of hydrocarbons
Flammability
Hydrocarbons with longer chains are less flammable.
Boiling point
Hydrocarbons with longer chains have higher boiling points.
Viscosity
Hydrocarbons with longer chains have higher viscosity (i.e. they are thicker and flow less easily).
What is cracking of hydrocarbons ?
Thermal decomposition reactions - Cracking is the process that breaks down long-chain hydrocarbons into shorter-chain molecules that are more useful
What is steam Cracking?
Vapourised heavy hydrocarbons are mixed with steam in a high temperature environment.The products include alkanes and alkenes.E.g. decane → octane + ethene
What is catalytic cracking ?
Vapourised heavy hydrocarbons are passed over the top of a heated catalyst.
Alkanes and alkenes are produced by this reaction.
E.g. hexane → butane + ethene
Why does combustion depend on oxygen avaliable ?
The equations for the combustion (burning) of hydrocarbons depend on the amount of oxygen that is available.
Problems with incomplete combustion ?
As well as producing carbon monoxide, incomplete combustion produces soot.
Soot can build up in appliances and cause problems. This happens in cars and any items that use carbon compounds as fuel.
Combustion burning with plenty of oxygen :
Burning with plenty of oxygen
The combustion (burning) of hydrocarbons when there is a good air supply involve:Energy release.The oxidation of carbon and hydrogen to create carbon dioxide and water.
Combustion burning with little oxygen - properties of carbon monoxide.
Burning with a lack of oxygen
If alkanes are burned without enough oxygen, then carbon monoxide can be created:2C + O2→ 2COCarbon monoxide is a gas with the following properties:ColourlessToxicOdourless
Impurities in fossil fuels - nitrogen oxides
Nitrogen oxides
When hydrocarbons are burned in a confined space (e.g. in the internal combustion engines of cars), the high temperatures can cause nitrogen and oxygen to react.
This leads to the formation of toxic nitrogen oxides.
Sulfur impurities in fossil fuels - contribution to acid rain.
Sulfur is an impurity that is present in all fossil fuels.Sulfur oxidises when burned. This produces the toxic gas sulfur dioxide.If inhaled, sulfur dioxide can cause respiratory (breathing) problems.Sulfur dioxide can react with water to form sulfuric acid, which is a major component (part) of acid rain.Acid rain causes steel corrosion, the weathering of buildings and statues, and the death of insects, plants, and aquatic organisms.
Advantages of hydrogen fuel cells over fuels ? (Sometimes in cars)
Advantage - toxicity
Hydrogen fuel cells use hydrogen and oxygen and the only waste product is water.This means no greenhouse gases are emitted. Petrol vehicles emit greenhouse gases into the atmosphere.
Advantage - capacity
Hydrogen fuel cells produce more energy per gram of hydrogen relative to petrol.
Disadvantages of hydrogen fuel cells
Disadvantages
But hydrogen has to be stored at a high pressure and hydrogen gas is explosive.There are not many places to refuel either.
What are the dangers of acid rain ?
Acid rain causes steel corrosion, the weathering of buildings and statues, and the death of insects, plants, and aquatic organisms.
