Alkanes
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- Created by: Rachael1
- Created on: 23-04-17 19:36
Explain the stages of fractional distillation?
Crude oil is heated, evaporates into the fractional distillation column, condences at different fractions depending of the number of carbon atoms in the chain. Longest chains have highest boiling points due to greater number of intermolecular forces.
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Explain trend in bond enthalpy of group 7?
decreases going down because they have more shells, shielding and so bonds they make are weak but very reactive
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Explain trend in bond polarity of group 7?
decreases going down because they are more electronegative at the top because they will attract electrons
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What does the melting point of halogenoalkanes depend on?
The longer the chain, the greater the van der waals forces and size of halogen, larger it is, greater van der waals forces
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What do curly arrows show?
movement of a pair of electrons
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What's a nucleophile?
A species which is an electron pair donor
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Which polluting product do engines not produce anymore?
Sulfur dioxide
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What polluting gases do catalytic converters reduce?
carbon monoxide, nitrogen oxides, unburnt hydrocarbons
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Explain the greenhouse effect?
visible rays pass through glass and are absorbed.They're reradiated as infrared energy which has a lower wavelength. Carbon dioxide traps it in this way.
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What's the problem using fossil fuels and what are they used for?
increases carbon dioxide and industrial plants
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Are alkanes reactive?
no, but they do react under suitable conditions
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What polluting products do hydrocarbons release?
Carbon diocide, carbon monoxide, sulfur dioxide-acid rain, nitrogen oxides-caid rain and photochemical smog, carbon particulates-asthma and cancer, unburnt hydrocarbons-smog,water vapour
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What does combustion of fossil fuels produce?
sulfur dioixde which causes acid rain with oxygen and water vapour
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What are the two reactions to remove sulfur dioxide from fossil fuels?
sulfur dioxide and water vapour and oxygen and calcium oxide to produce calcium sulfite which can be further oxidised to calcium sulfate. sulfur dioxide and oxygen and calcium carbonate producing calcium sulfate and carbon dioxide.
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What's calcium sulfate used for?
make builders plaster and plaster board
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what pollutant is removed from petrol before its used?
sulfur
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What shape are catalytic converters and what are they made of?
honeycomb- platinum and rhodium, providing an enormous surface area so little of these expensive metals goes a long way
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Write an equation of when polluting gases are passed over the catalyst?
carbon dioxide and nitrogen oxide react to give nitrogen gas and carbon dioxide
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Explain how water vapour can act as a greenhouse gas in the atmosphere?
concentration of iis roughly the same due to equilibrium, higher temp of earth, more water vapour
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How could water vapour be offset?
cloud formation or clouds reflecting solar radiation
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What's more economically valuable between long chain and short chain hydrocarbons?
short chain hydrocarbons because they are useful as petrol and some of the product of cracking are alkenes which are used as chemical feedstock, converted into others like plastics(polymers),pains, drugs
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In what two methods can we break alkanes?
thermal cracking and catalytic cracking
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what happens during thermal cracking?
high temps and pressures, alkene produced
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What happens during catalytic cracking?
lower temps and pressures, uses a zeolite catalyst (silicon dioxide and aluminium) they have a honeycomb structure with enormous surface area
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What does catalytic cracking produce?
branched alkanes, motor fuels, cycloalkanes,aromatic compounds. They are mostly gases showing short chains up to C5 and the mixture decolourises romine solution
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Characteristics shared between the homologous series?
same general formulas, same functional group, similar chemical properties
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What other functional group isomer can alkenes have?
cycloalkanes
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What's sterioisomerism?
same structural formula but different arrangement of bonds in space
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Suggest why the branched chain isomer has a lower boiling point than octane?
there's less surface area and therefore less surface contact so there's weaker van der waals forces between the molecules
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Other cards in this set
Card 2
Front
Explain trend in bond enthalpy of group 7?
Back
decreases going down because they have more shells, shielding and so bonds they make are weak but very reactive
Card 3
Front
Explain trend in bond polarity of group 7?
Back
Card 4
Front
What does the melting point of halogenoalkanes depend on?
Back
Card 5
Front
What do curly arrows show?
Back
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