Developing Fuels Flashcards
Why does MTBE produce less carbon monoxide when burnt that pentane
There is less incomplete combustion as the molecule is already partially oxidised
Describe how a heterogeneous catalyst works
The reactant is adsorbed to the surface of the catalyst
Intramolecular bonds are weakened and broken
New bonds form
The product diffuses off the surface
What’s a structural isomer
a molecule with the same molecular formula but different structural formula
What is a biofuel and why is it carbon neutral
Made from crops which can be replanted
Plants take in CO2 for photosynthesis
Which balances out the CO2 produced from burning
Explain what is meant by auto-ignition and why it is undesirable in an engine.
Fuel igniting to without a spark which can damage the engine
You have a simple methane molecule, what is the shape, the bond angles and why? (5 points)
Tetrahedral 109 degrees 4 areas of negative charge that repel each other as far as possible
What does octane measure and why is it desirable to increase the number.
Measures the tendency to knock, higher the octane number means less knocking
Name 2 products formed by reforming
cycloalkanes and cycloalkenes
Explain how the catalyst can be poisoned by lead
The lead stays on the catalyst which prevents other molecules from reaching the surface
Suggest a benefit of using hydrogen as fuel
only produces water or does not produce CO2
Use ideas of bondmaking and bondbreaking to explain how a reaction can be endothermic
Bond breaking takes in energy, bondmaking gives out energy, here less energy is being given out then taken in
Explain what happens in cracking reactions and what types of molecules are produced
a large hydrocarbon is split into shorter alkanes and alkenes
Suggest why the use of non-food parts of crop plant is desirable for the production of biofuels
Allows food crops to be used for food
Production of food not affected
Give 2 ways in which molecules formed by cracking of a straight chain alkane molecule differ from the original molecule.
Shorter Hydrocarbons
Unsaturated/Alkenes
Explain the term catalyst and name the type of catalysis used in cracking
Catalysts speed up a reaction and be recovered unchanged/ not used up
Provide a path of lower activation energy
Heterogeneous catalysis
Describe and explain the structural feature of zeolites that make them effective catalysts for the cracking process.
Heterogeneous catalysis occurs on surface (ADSOBED)
Large surface area
Name the refining process used to convert straight chain alkanes into branched chain alkenes with the same number of carbon atoms.
Isomerisation
One method of disposing of used oil is to burn them. However, this produces atmospheric pollution in the form of a dense black cloud of Carbon particulates
Suggest and explain how these particulates are formed.
Incomplete combustion of oil
Caused by insufficient supply of oxygen
What does empirical formula show
It shows the smallest ratio of the different atoms present
Is it more desirable have a low or high octane number
High
What type of hydrocarbons have high octane numbers
Those with lots of branched chains and aromatic rings and generally shorter
What catalysts and conditions are used in isomerisation
Platinum at 260 Celsius and then the products are passed over a zeolite sieve separating the straight from the branched
Suggest one reason why the use of non food parts of crops is desirable
Production of food is not effected
What pieces of info are needed to workout the enthalpy change of combustion
Mass of fuel
Mr of fuel
Vol of water
Specific heat capacity
What are the two products of reforming
Cyclic hydrocarbons and hydrogen
What is a structural isomer
Different structural formulae for the same molecular formula
