Alkanes Flashcards
What is the general formula for an alkane?
CnH2n+2
State the mixtures from top to bottom in order
Refinery Gases don't condense Gasoline Naptha Kerosene Diesel oil Fuel oil Residue (long hydrocarbons)
How does fractional distillation work?
The vaporised oil enters the column in which there’s a temp. gradient. Cooler at the top. At the top, low viscosity, more flammable due to a low activation energy.
Explain how global warming arises
Burning fossil fuels produces CO2 (greenhouse gas). CO2 absorbs infra red radiation (heat) from sun but emits some back onto earth (greenhouse gas effect). Increasing amount of CO2 - increasing global temps - Global Warming
How does Carbon Monoxide form and state it’s effect
This is formed via Incomplete Combustion which Is poisonous to humans and contributes to the greenhouse effect
How do unburnt hydrocarbons form and state the effects
They are formed when the engine is no hot enough or inefficient and irritate the lungs and react photochemically with sunlight to produce smog
How do Oxides of Nitrogen form and state the effects of them
Formed by N2 + O2 –> 2NO at high temperatures in engines. It can combine with water to produce nitric acid; component of acid rain or contribute to photochemical smog
What are catalytic converters?
They can remove the pollutants (Carbon Monoxide, Unburnt Hydrocarbons, Oxides of Nitrogen). They have a honey comb structure and is coated with a thin layer of platinum; increasing surface area.
Why is cracking useful?
This is when we crack heavier fractions into smaller, more useful ones and there is a demand for smaller ones
Explain the conditions of Thermal Cracking and the products?
High temperatures (900°C) 700kPa Steam Homolytic Products are alkenes which can be used as chemical feedstock and conversion to polymers (plastics)
Explain the conditions of Catalytic Cracking and the products
High temperatures (450°C) Slight pressure Zeolite catalyst to lower temp needed Heterolytic Products are branched alkanes, cycloalkanes
Explain how Flue Gas Desulphurisers works
In the first step, forms Calcium Sulphite
SO2 + CaO –> CaSO3
It is then oxidised by oxygen into Calcium Sulphate (gypsum and is used as plaster)
CaSO3 + 1/2O2 –> CaSO4
Explain what Sulphur - containing impurities can lead to
Fossil fuels contain Sulphur impurities, when the file burns, Sulphur is combusted to form Sulphur dioxide.
S + O2 –> SO2
The gas reacts with water to form sulphurous acid
SO2 + H2O –> H2SO3
What distinguishes whether an elimination reaction happens or substitution
alkene will form if ethanol used as solvent or alcohol if water is used as the source of OH ions
What is produced from catalytic cracking?
|> Aromatic Rings (e.g. Benzene)
Motor Fuels
Aromatic Hydrocarbons
