DF 3 - what's in your tank Flashcards
specification reference - (l) (m) (r)
what is petrol and diesel a mixture of
many different compounds carefully blended to give the right properties.
how are the compounds in petrol and diesel for e.g obtained
from crude oil
what is crude oil
a mixture of hydrocarbons. a thick black liquid with gases and solids dissolved in it.
how is crude oil obtained
oil from the north sea is pumped along pipes on the seabed to UK refineries and special tankers bring curde oil from distant oilfields. (Middle East & Alaska). these refineries are either close to the shore is the oil is off-loaded into a pipeline leading to a refinery
what can crude oil also contain
small amounts of other compounds and may contain sulfur
when the sulfur in the crude oil is burnt it produces sulfur dioxide which can lead to acid rain
how is crude oil separated by
fractional distillation
why does crude oil need to be separated
it isn’t useful as a mixture (different hydrocarbons make up the mixture)
which hydrocarbon does crude oil mostly contain
alkanes
how is the mixture separated
into fractions based on their boiling point
what does each fraction consist of
similar chain length hydrocarbons with similar boiling point
what determines which fraction each hydrocarbon molecule will be separated into
the size and length of each hydrocarbon molecule. the size of each molecules relates to how many carbon and hydrogen atoms molecules contain
where is fractional distillation carried out
in a fractionating column
what does the fractionating column contain
a temperature gradient - its hot at the bottom and cool at the top
describe the process of fractional distillation
- crude oil enters the fractionating column and is heated so vapours rise.
- hydrocarbons with high boiling points condense in higher temperatures at the bottom of the column
- hydrocarbons with low boiling points condense in lower temperatures at the top of the column
- the condense and tap off as liquids
what are the hydrocarbons at the top of the fractionating column most likely to be
gases
where are the bigger hydrocarbons usually located in the fractionating column
at the lower sections of the fractionating column
what is needed for fractional distillation to occur
heat
do the fractions have an exact boiling point
no because they are mixture of different hydrocarbons
which fractions are the sources of petrol components
the gasoline and gas oil fractions
how many electrons does carbon have in its outer shell
4 electrons
how could carbon achieve stability theoretically
by losing or gaining 4 electrons
why cant carbon gain or lose 4 electrons
this is too many electrons to lose or gain. the ions would have a very high charge
which bonds do carbon compounds form
covalent
how does the carbon in methane achieve stability
the carbon atoms acheives stability by sharing its outer electrons with four hydrogen atoms forming four C-H covalent bonds
what can carbon form when forming strong covalent bonds with itself
chains and rings of its atoms joined by C-C covalent bonds
what is catenation
Catenation is the self-linking of atoms of an element to create chains and rings.
how many covalent bonds can a carbon atom form
4
what is special about the chains of carbon
the chain may be straight or branched and can have other atoms or groups substituted on them
what is a hydrocarbon
chemicals which are only made up of carbon and hydrogen atoms
how are the carbons and hydrogen atoms arranged in hydrocarbons
the carbon atoms are joined into chains of different lengths. the hydrogen atoms come off the carbon atoms
name the different types of hydrocarbon
alkanes
alkenes
arenes
cycloalkanes
what is benzene
it is an arene with formula C6H6.
it is a ring with six carbon atoms. inside the ring is an area of delocalised electrons
what are aromatic compounds
compounds that contain a benzene ring
what are aliphatic compounds
compounds that do not contain benzene ring
which hydrocarbons form the unreactive framework of organic compounds
alkenes and arenes
what is an alkane
unsaturated hydrocarbons containing single bonds
what do alkanes end in
-“ane”
what is the general formula for alkanes
CnH2n+2
name the first four alkanes and their molecular formula
methane - CH4
ethane - C2H6
propane - C3H8
butane - C4H10
what is a homologous series
a family of organic compounds with the same functional group but a different carbon chain length. they have the same general formula and each member differs to the next by a CH2 group
how does the length of the carbon chain affect reactivity and physical properties
it has little effect on the reactivity of the functional group but it will affect physical properties such as melting point, boiling point and solubility
what is a functional group
Functional groups are specific groups of atoms that are present within organic molecules and are responsible for the characteristic properties and reactivity of those molecules.
what is a general formula
A type of empirical formula that represents the composition of any member of an entire class of compounds.
what is a molecular formula
tells you how many atoms of each type are present in a molecule of the compound
what is an empirical formula
gives the simplest ratio of the different types of atoms present
what is a structural formula
formula which shows the arrangement of atoms in the molecule of a compound but does not show all the bonds between them.
what is a skeletal formula
representation of molecular structure in which covalent bonds are shown as lines.
The symbols for all elements other than carbon and hydrogen are always drawn
what is a cycloalkane
Cycloalkanes are the class of hydrocarbons having a ring-like structure. they are saturated
give the first four cycloalkanes
cyclopropane
cyclobutane
cyclopentane
cyclohexane
give the general formula of cycloalkanes
CnH2n (same as alkenes)
what is different about cycloalkanes
they have two fewer hydrogens than the corresponding alkane
do alkanes have straight or branched chains
they can have either
what is the connection between a straight chain compound and a branched chain compound
it is often possible to draw more than one structural formula for a given molecular formula. there is often a straight chain compound and one ore more branched chain compounds with the same molecular formula
what is a structural isomer
a compound with the same molecular formula but different structural arrangement of atoms
give example of two isomers
butane and methylpropane
- both have molecular formula C4H10
what is an alkyl group
if you remove a hydrogen from an alkane you get an alkyl group
this is what forms the side chains in branched alkanes
name the first ten alkyl groups
methyl
ethyl
propyl
butyl
pentyl
hexyl
heptyl
octyl
nonyl
decyl
what prefix do we add on if there is more than side chain
di = two
tri = three
tetra = four
rules for naming branched alkanes
1) find the longest chain of carbons (5 carbon = pentane etc)
2) identify any side chains off the main chain
3) name these side chains
4) state the location of these side chains and keep the number as low as possible (if its on carbon 2, 3 etc)
5) if there is more than one side chain keep the numbering as low as possible. name them in alphabetical order (2-ethyl, 3 methyl for e.g)
6) if there are more than one of the same side chain use the prefixes di, tri, tetra
7) name the compound by starting with the side chains, location of them, the parent chain
8) use hyphens between numbers and letters and commas between numbers
2,2,3 - trimethylbutane
four carbon atoms —> butane
3 side chains - all methyl –> tri
two are located on carbon 2, one is located on carbon 3
2,2,3 - trimethylbutane
3-ethyl, 2-methylpentane
five carbon atoms –> pentane
2 side chains - 1 ethyl and 1 methyl
write in alphabetical order –> ethyl, methyl
ethyl on carbon 3, methyl on carbon 2
3-ethyl, 2-methylpentane
how do we name cycloalkanes
have general formula - CnH2n
1) count the number of carbons in the cyclic structure and identify the appropiate prefix to name the alkane
2) add the alkane name to the end of cyclo
what is an arene
unsaturated ring structure with general formula CnHn
what is an alkene
unsaturated compounds with at least one carbon-carbon double bond
general formula of alkenes
CnH2n
name the first few alkenes
ethene - C2H4
propene - C3H6
but-1-ene - C4H8
but-2-ene - C4H8
pent-1-ene - C5H10
pent-2-ene - C5H10
what is the difference between but-1-ene and but-2-ene
double bond is on carbon 1 on but-1-ene
double bond is on carbon 2 on but-2-ene
3-methylhex-2-ene
six carbon atoms –> hex
hex-2-ene —> the double bond is on carbon 2
methyl side chain on carbon 3 - 3methyl
3-methylhex-2-ene
what is the differenct between Z-But-2-ene and E-But-2-ene
in Z-but-2-ene the methyl groups are on the same side of the double bond
in E-but-2-ene the methyl groups are on opposite sides of the double bond
how else is Z-but-2-ene and
E-but-2-ene named
Z –> cis-2-butene
E –> trans-2-butene
what is 1,4-cyclohexadiene
6 carbon atoms - cyclohexene
two double bonds so its diene
—> cyclohexadiene
one double bond is on carbon 1 and the other is on carbon 4
general formula of alcohols
CnH2n+1OH
name the first few alcohols
methanol - CH3OH
ethanol - C2H5OH
propanol - C3H7OH
butanol - C4H8OH
what is the difference between propan-1-ol and propan-2-ol
in propan-1-ol the OH is on carbon 1
in propan-2-ol the OH is on carbon 2
rules for naming alcohols
1) name the alcohol using the root prefix of the longest chain
2) determine the position of the alcohol group -OH by counting the carbons to give the lowest number
3) Add -ol onto the end of the name
how do we name an alcohol if its branched
just follow the rules for a branched alkane but replace the e at the end with ol and include the number the OH group is attached to
2-methylpropan-1-ol
3 carbons –> prop
OH is on group 1 –> propan-1-ol
methyl side chain on carbon 2 –> 2-methyl
2-methlypropan-1-ol
ethan-1,2-diol
two carbon atoms –> eth
two OH groups –> diol
one OH group on carbon 1, one OH group on carbon 2
ethan-1,2-diol
2-3dimethylbutan-1-ol
4 carbon atoms –> but
OH on carbon 1 –> butan-1-ol
two side chains (both are methyl)
–> dimethyl
one side chain on carbon 1, the other on carbon 3 –> 2-3
2-3dimethylbutan-1-ol
what is the difference between saturated and unsaturated hydrocarbons
Saturated hydrocarbons contain only single covalent bonds while unsaturated hydrocarbons contain at least one or more double or triple carbon-carbon bonds.
