Chemistry: Basic Concepts and Hydocarbons

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  • Created by: meganlyy
  • Created on: 04-01-18 19:17
Definition of homologous series.
Molecules which have the same functional group and general formula.
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What do members of a homologous series differ by?
CH2
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What are aromatic compounds?
Compounds containing benzene ring.
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What are non-aromatic compounds called?
Aliphatic
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Definition of structural isomers.
Have the same molecular formula but different structural formula.
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Name the three types of structural isomers.
Chain isomers, positional isomers, functional group isomers.
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What shape and bond angle does an alkane form around each carbon?
Tetrahedral shape, bond angle 109.5 degrees.
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Why do smaller alkanes have a lower boiling point?
Alkanes have Van der Waals between the molecules. Longer the chain, stronger the forces as there is more surface contact and more electrons to react.
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Why do branches chains have lower boiling points than straight chain alkanes?
Branched chains can't pack as closely as straight chains so there's a smaller molecular surface area.
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What reacts together in a combustion reaction for alkanes, and what is formed?
Oxygen and alkane, carbon dioxide and water formed.
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What do liquid alkanes have to go through before they can react in a combustion reaction?
Combustion reactions only happen between gases so liquid alkanes have to be vaporised first.
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Why are larger alkanes better fuels?
Larger alkanes release a lot more energy as there are more bonds which react.
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What is formed in incomplete combustion?
Carbon monoxide and water.
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What are the two ways a single bond can break?
Heterolytic fission and homolytic fission.
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Describe heterolytic fission.
Bond breaks unevenly as one atom receives both electrons. Cation and anion formed.
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Describe homolytic fission.
Bond breaks evenly as both atoms receive one electron. Two electrically uncharged radicals are formed (radicals are atoms that have an unpaired electron).
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When alkanes react with halogens, what is formed and what type of reaction occurs?
Haloalkanes are formed in a free-radical substitution reaction.
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What does a free-radical substitution reaction need to start reacting, and how does it start?
Ultraviolet light is needed as it breaks the Cl-Cl bond (photodissociation) and forms two free radicals.
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What is the problem with free-radical substitution?
Forms a mixture of products. and can occur anywhere along the carbon chain so end up with mixture of isomers.
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What is a double bond made up of?
Pi bond and Sigma bond.
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Describe a sigma bond.
Overlap of two s-orbitals. High electron density between two nuclei meaning strong electrostatic attraction between nuclei and shared electrons. Have high bond enthalpy and are strong covalent bonds.
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Describe a pi bond.
Formed by overlap of two p-orbitals which is in shape of a dumb-bell. Means electron density is spread out above and below molecule so electrostatic attraction between nuclei and electrons is weaker.
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What two factors make double bonds reactive?
Double bond contains high electron density and pi bond sticks out above and below molecule.
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What shape and bond angle do alkenes make around each carbon?
Trigonal planar shape, bond angle 120 degrees.
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Why can't double bonds rotate?
Carbons in double bond and atoms attached are all in the same plane.
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What causes stereoisomers?
Restriction around double bond, and rotation around single bonds.
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Definition of stereoisomers.
Stereoisomers have the same structural formula but have different arrangement in space.
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When is E/Z naming used?
When the same groups are on the same side of the double bond Z is used and when the same group is on opposite sides of the double bond E is used.
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How do you name stereoisomers with all different groups?
The atom with the highest atomic number on each carbon is given priority. If these are on the same side of the double bond it's a Z isomer, if it's not it's a E isomer.
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When is Cis/Trans naming used?
Used when both carbon atoms have at least one group in common. Cis is when theyre on the same side and Trans is when they're on opposite sides.
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What type of reaction do alkenes go through?
Electrophilic addition because pi bond creates high electron density and double bond can open up and accept atoms.
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What are electrophiles?
Electron pair acceptor, include positively charged ions or polar molecules.
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How do you make an alkane from an alkene, and what are the conditions?
Reagent is H2 and conditions are nickel catalyst, 150 degrees.
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What is made when halogens react with alkenes?
Dihaloalkanes.
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How are alcohols made from alkenes, and what are the conditions?
React alkene with steam and conditions are 300 degrees, 60-70 atm pressure, solid phosphoric(V) acid catalyst.
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What is formed when alkenes react with hydrogen halides, and what happens if the alkene is unsymmetrical?
Haloalkanes, and will form two products if alkene is unsymmetrical.
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What makes a carbocation more stable?
If there are more R groups attached then it is more stable.
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What is Markownikoff's rule?
The major product formed from addition of hydrogen halide to an unsymmetrical alkene is the one where H attaches to the carbon with the most Hs already attached.
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What is the reaction called when alkenes join up to make a polymer?
Addition polymerisation.
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What is the advantage and disadvantage of plastics being unreactive?
Will not react with food but makes it really difficult to dispose of.
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What are the four ways waste plastics can be disposed of?
Buried in landfills, recycled and remoulded, cracked into monomers and burned to create electricity.
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How do biodegradable plastics decompose?
Microorganisms feed off of them.
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Other cards in this set

Card 2

Front

What do members of a homologous series differ by?

Back

CH2

Card 3

Front

What are aromatic compounds?

Back

Preview of the front of card 3

Card 4

Front

What are non-aromatic compounds called?

Back

Preview of the front of card 4

Card 5

Front

Definition of structural isomers.

Back

Preview of the front of card 5
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