(YELLOW) alkanes Flashcards
(YELLOW) alkanes
what is the definition of hydrocarbon
Hydrocarbons compounds containing carbon and hydrogen only.
what is the name give to carbon that can form chains and rings called
catenation
what is the electronic configouration of carbon
1s2 2s2 2p2
why does silicon not replace carbon in organic matter
silicon is just too big
what is homologous series
Homologous series A family of compounds with the same functional group, which differ in formula by CH2 from the next member.
give examples of homologous series
alkene , alkane , carboxilic acid . alcohols , alkalines , esters , amino acids
what is a functional group
Functional Group
the atom or group of atoms responsible for the chemical behaviour of the molecule
what is the definition of empirical formula :
Empirical formula shows
The simplest whole number ratio of atoms present in the molecule.
e.g. C5H12
what is the definition of Molecular formula
Number of each kind of atom present in the molecule
e.g. C5H12
what is the definition of Structural formula
Structural formula shows
the functional groups present and how the atoms are linked
e.g. CH3CH2CH2CH2CH3
what is the definition of Displayed formula
Displayed formula shows
all the covalent bonds single bonds as a line, double bonds as C=C and triple bonds as C≡C. All H atoms must be shown.
what is the definition of Skeletal formula
Skeletal formula
Omit C atoms and H atoms, - is a single bond, = a double bond and ≡ is a triple bond
if there is another atom present then it is shown.
what are the names given to chain lengthens from 1 to 10
1 methane
2 ethane
3 propane
4 butane
5 pentane
6 hexane
7 heptane
8 octane
9 nonane
10 decane
what are the four rules of naming compounds
If there are several branches of different lengths they are put in alphabetical order. i.e. ‘ethyl’ before ‘methyl’ before ‘propyl’.
If there are several branches of the same length the number of branches is shown by a prefix and the position of every branch is indicated by a number before the name:
hyphens go between numbers and letters
commas go between numbers
what is a structural isomerism
STRUCTURAL ISOMERISM occurs when two or more compounds have the same molecular formula but different structural formulae.
waht is the general trend in boiling points when you increase chain length of an alkene
increase
are alkanes soluable in water
and what would you expect to see
no
2 layers
watch vids on fractional distilation and cracking there is nothing really much on it just have to know about it and what it does
what is cracking in alkanes
Cracking is the breakdown of molecules into shorter ones by heating with a catalyst.
what is reforming
Reforming is the conversion of straight chained hydrocarbons into branched and cyclic hydrocarbons by heating with a platinum catalyst.
normally produces hydrogen as a sub-product
Why is crude oil so important?
Used as fuel and lubricants, valuable source of chemicals
These are used for the manufacture of paints, polymers, pharmaceuticals etc.
Why should we try to conserve our reserves of crude oil?
They are a finite resource and a valuable source of chemicals
Why is cracking important?
Cracking increases our supplies of the gasoline (petrol) fraction and produces short chain alkenes that are used to manufacture polymers (plastics)
What conditions are used for cracking?
High temps >400oC, needed for zeolite catalyst, moderate pressure to move gases through the system
Why are governments around the world becoming increasingly concerned about our use of fossil fuels?
Combustion of fossil fuels —> greenhouse gases —> global warming, acid rain, smog.
They are a finite resource
Suggest three ways in which our use of fossil fuels might be reduced
Alternative energy sources – wind, solar, tidal, hydroelectric, biofuels, nuclear
Reduce energy consumption
Recycling
What is the greenhouse effect?
CO2 and CH4 gases in the atmosphere act as a blanket preventing solar energy being re-radiated back out to space
How do CO2 levels relate to climate change
CO2 increases global warming —-> melting glaciers,sea ice —> sea level rises
More energy in atmosphere —> more violent storms; seas warming —-> sea level rises
Biofuels are sometimes described as ‘carbon neutral’. Why is this?
Plants photosynthesise using CO2 —> biofuels
Burning these biofuels only releases the original CO2 back into the atmosphere
Explain what is meant by ‘sustainable development’, using examples from the manufacture of fuels.
Does not use up non-renewable or finite resources
Does not produce large amounts of waste which could have an environmental effect, e.g CO2 —-> climate change, waste bottles, polymers, packaging —-> landfill.
info card
Sulfur occurs naturally in crude oil, and although most of it is removed in the formation of petrol it is impossible to remove all the sulfur. During combustion these atoms of sulfur are converted into sulfur dioxide.
Give the reaction of sulfur reacting to form sulphur dioxide
S + O2 —> SO2
The sulfur dioxide can then react to form sulfur trioxide
2SO2 + O2 —-> 2SO3
Give the equation for the reaction of Nitrogen dioxide and water
2NO2 + H2O —-> HNO2 + HNO3
Which pollutant is not removed via the catalytic converter?
Sulfur
Note that no fuel is currently 100% carbon neutral why?
Energy in the form of (usually) fossil fuels are still used in the manufacturing and transportation of the biofuel
what is the general eqation for an alkane reacting with chlorine in ultraviolet radiation
use methane as the alkane
what type of reaction is this
CH4 + Cl2 —> CH3Cl + HCl
has to be in concentrated chlorine
free radical substatution
what are the three steps of free radical substitution
ultravoilet
UV light breaks the chlorine molecule which produces two chlorines with one unpaired lone pair
what is the definition of HOMOLYTIC FISSION
HOMOLYTIC FISSION (homo- of like kind, lysis-to break open) is the term used to describe the breaking of a covalent bond so that the bonding electrons are shared equally between the atoms involved. It is represented using half-headed curly arrows.
what are free radicals
FREE RADICALS are molecular fragments or atoms with one unpaired electron.
They are highly reactive.
what is a substitution reaction
SUBSTITUTION REACTION where one atom or group of atoms replaces another atom or group of atoms
draw out the propagation step for chlorine free radical with methane
and also the step in which the free radical is regenarated
https://crunchchemistry.co.uk/free-radical-substitution-reactions/
