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36 Cards in this Set
- Front
- Back
what does nomenclature mean? |
the naming of molecules using specific rules |
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Functional group |
the group of atoms responsible for the characteristic reactions of a molecule |
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what is a general formula? what is a homologous series? |
an algebraic formula which describes any member of a family of compounds. e.g alkanes general formula is CnH2n+2 A family of compounds which have the same functional group and general formula. |
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what is molecular formula |
shows the actual number of atoms of each element in a molecule. |
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what is empirical formula |
the simplest whole number ratio of atoms of each element in a compound. |
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what is structural formula? |
example: ch3ch3 |
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what is displayed formula? |
shows how atoms are arranged |
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skeletal formula |
shows the bonds of the carbon skeleton only with functional group |
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what does a benzene molecule look like? |
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what is an aliphatic compound? |
contains only carbon and hydrogen joined together in strait,branched or non-aromatic rings. if an aliphatic compound contains a non aromatic ring then it can be called alicyclic. |
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what is an alkyl group |
(in a compound) it is any branched hydrocarbons. it has the general formula CnH2N+2 |
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what is a chain isomer? |
same atoms as another molecule but different arrangement of the carbons |
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what is a positional isomer |
when functional group is in a different place |
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what is a functional group isomer? |
same atoms except they are arranged into different functional groups |
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what are the prefixes for carbon 1,2,3,4,5,6? |
1-methyl these show how many 2-ethyl branches there are 3-propyl 4-butyl 5-pentyl 6-hexyl |
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what is the shape of an alkane molecule? |
each carbon will have 4 pairs which will repel each other equally so it forms a tetrahedral shape with a bond angle of 109.5 |
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what is the bonding in an alkane? |
the C-C and C-H bonds are all single covalent and can overlap forming a covalent bond between two atoms. if the overlap good it will be a stronger bond. This is a sigma bond. ( strongest covalent bond) |
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explain the unreactive nature of alkanes |
The C-C and C-H sigma bonds have very large bond enthrapy making them very strong and difficult to break. they are also non polar so won't attract any positive or negatively charged particles to react with them. |
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explain the trends in boiling point of alkanes |
the larger the alkane the higher the boiling point as although covalent bonds hold the alkanes together it is induced dipole-dipole interactions inbetween alkanes so the longer the chain the more induced D:D reactions their are. |
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which has a lower boiling point, branched or unbranched alkanes? and why? |
Branched as they can't pack together as closely and they have smaller surface areas so induced D:D ineractions are reduced |
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complete combustion of propane( alkane) |
C3H8+502--------3C02+4H20 co2 and water is formed. they are also good fuels as they release lots of energy when bonds are broken |
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incomplete combustion of methane |
2CH4+302-------2CO+4H20 This can cause carbon monoxide poisoning which binds to haemaglobin |
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what is Heterolytic fission? |
when the bomd breaks unevenly so one atom has 2 electrons while the other has none. it forms a cation and an anion. XY----X+ + y- |
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What is homolytic fission? |
when the bomd breaks evenly so each atom gets 1 electron in a bonding pair. Radicals are formed. XY---- X. +Y. |
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what does the curly arrow show? |
the movement of electrons |
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How are haloalkanes formed? |
when alkanes react with halogens. It is a photochemical reaction( started by light). They produce a free radical |
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what are the stages in the synthesis of chloromethane and explain them |
initiation 1. photodissociation( cl-cl bonds break forming radicals) propogation 2. CL.+CH4-------CH3.+HCL that can then attack a cl. and so on. Termination 3. 2 radicals come together to make a stable molecule. |
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what are alkenes and what are there general formula? |
carbon and hydrogen atoms only. have at least one unsaturated/ double bond. CnH2n end in ene |
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what is the bond structure of an alkene |
it is a double bond( sigma and pi bond). The sigma bond forms forms by two orbitals overlapping in a strait line to give the highest possible electron density between the two. the pie bond is formed when two p orbitals overlap sideways( dumbell shape) |
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why are pie bonds weaker than sigma bonds |
they are spread above and bellow nuclei so attraction between nuclei and electrons is weaker so have low bond enthrapy which is why double bond are not twice as strong as single bonds. |
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Are alkenes reactive or unreactive and why? |
Are reactive due to the 2 pairs of electrons in the bond and as the pie bond has a low bond enthrapy |
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what shape is an alkene |
trigonal playnar so 120 degrees |
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what is a stereoisomer and why can an alkene be one? |
when it has the same structural formula but a diffrent arrangent in space. Because c=c bonds mean atoms cant rotate |
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when is it an E isomer and when is it a Z isomer? |
E=when the highest priority groups are on diffrent sides Z= when the highest priority group is on the same side |
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what are the priority rules when working out E-Z isomerism? |
-H is the lowest priority group - the one with the highest priority i sthe one with the highest atomic number(it must be directly bonded to a carbon) |
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when ís cis/trans used and how do we know if its cis or trans? |
when the two carbon atoms either side of the double bond have at least one group in common Cis- two identcal groups on same side Trans-two identical groups on opposite sides |