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Chemistry Alevel OCR > 4.1 Basics Concepts And Hydrocarbons > Flashcards

4.1 Basics Concepts And Hydrocarbons Flashcards

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1
Q

What are the stem names for the first ten alkanes based on number of carbons?

A

1 carbon= meth-
2 carbons= eth-
3 carbons= prop-
4 carbons=but-
5 carbons=pent-
6 carbons=hex-
7 carbons=hept-
8 carbons=oct-
9 carbons=non-
10 carbons=dec-

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2
Q

What is nomenclature?

A

The system for naming compounds

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3
Q

Define a homologous series

A

A series of organic compounds having the same functional group but with each successive member differing by CH2

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4
Q

What are the names of the alkyl groups depending on their number of carbons?

A

1carbon= methyl-
2carbons=ethyl-
3carbons=propyl-
4carbons=butyl-
5carbons=pentyl-
6carbons=hexyl-
7carbons=heptyl-
8carbons=octyl-
9carbons=nonyl-
10carbons=decyl-

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5
Q

What is the general formula for an alkyl group?

A

CnH2n+1

-n=number of carbons

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6
Q

What is the general formula for alkanes?

A

CnH2n+2

-n=number of carbons

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7
Q

What is the general formula for alkenes?

A

CnH2n

-n=number of carbons

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8
Q

What is the general formula for an alcohol?

A

CnH2n+1 OH

-n=number of carbons

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9
Q

What is an aliphatic compound?

A

-a compound containing carbon and hydrogen joined together in straight chains,branched chains or non-aromatic rings

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10
Q

What is an alicyclic compound?

A

-an aliphatic compound arranged in non-aromatic rings with or without side chains

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11
Q

What is an aromatic compound?

A

A compound containing a benzene ring

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12
Q

What is a structural isomer?

A

Compounds with the same molecular formula but different structural formulae

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13
Q

What are the 3 ways structural isomers can happen?

A

-the alkyl groups are in different places
-the functional group can be bonded to different parts of the parent chain
-the functional group could be different

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14
Q

Define stereoisomers

A

-organic compounds with the same molecular formula and structural formula but having different arrangements of atoms in space

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15
Q

What is homolytic fission?

A

-each bonding atom receives one electron from the bonded pair, this forms 2 radicals

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16
Q

What is heterolytic fission?

A

-one bonding atom receives both electrons from the bonded pair.

-this results in a cation and anion being formed

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17
Q

What is a radical?

A

A species with an unpaired electron

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18
Q

What are alkanes?

A

They are saturated hydrocarbons that contain single C-C and C-H bonds as sigma bonds (single)
They are free to rotate

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19
Q

What is a sigma bond?

A

An overlap of orbitals directly between the bonding atoms

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20
Q

What shape and bond angles do alkanes have?

A

-they have a tetrahedral shape with a bond angle of 109.5

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21
Q

What intermolecular bonding do alkanes have?

A

-carbon and hydrogen have very similar electro negativity values so alkane molecules are non-polar
-however as electrons are constantly moving at times there may be a lack of balance in charge distribution, causing an instantaneous dipole which will induce dipoles in neighbouring molecules
-this is called an induced dipole-dipole interaction or London force

22
Q

What happens to the boiling points of alkanes as the carbon-chain length gets longer?

A

-as an alkane chain gets longer its molecular mass increases
-larger molecules also have more surface area contacts between adjacent molecules
-this increases the number of induced dipole-dipole interactions (London forces)
-so more energy is needed to overcome the intermolecular attraction so that the alkane can change state ,so the boiling point becomes higher the longer the carbon-chain length is

23
Q

What effect does branching have on the boiling point of alkanes?

A

-the more branched a compound is the fewer surface interactions there are between molecules
-therefore branched molecules have fewer induced dipole-dipole interactions compared to a straight-chain isomer with the same molecular formula
-so branched molecules will have a lower boiling point than the equivalent straight chain isomer

24
Q

Why do alkanes have a low reactivity with many reagents ?

A

-all the covalent bonds in alkane molecules have high bond enthalpies- so a large amount of energy is required to break the bonds

-the carbon-hydrogen sigma bonds have a very low polarity as the electronegativities of carbon and hydrogen are almost the same

25
Q

What is complete combustion?

A

-there is a plentiful supply of oxygen and both carbon and hydrogen are oxidised
-it transfers the maximum amount of thermal energy

26
Q

What is the equation for the complete combustion of methane ?

A

CH4 + 2O2———> CO2 + 2H2O

27
Q

What is incomplete combustion?

A

-when an alkane is burnt in a limited supply of oxygen
-it produces carbon particles (soot) , water , carbon dioxide and carbon monoxide (CO)

28
Q

What are some chemical equations that can be used to show the incomplete combustion of methane?

A

2CH4+ 2 1/2 O2 → CO + C + 4H2O

2CH4 + 3 1/2 O2 → CO2 + CO + 4H2O

3СH4 + 4 1/2 O2 → CO2 + СО + С + 6Н2O

29
Q

What are some of the potential dangers from carbon monoxide (CO)?

A

-Is a toxic gas which is colourless and odourless
-it binds to heamoglobin and reduces the oxygen-carrying capacity of blood

-victims can lose consciousness and even die

30
Q

What are the conditions needed for alkanes to undergo radical substitution to form a radical ?

A

-ultraviolet light

-or temperatures of about 300 degrees Celsius

31
Q

What are Alkenes?

A

-they are unsaturated hydrocarbons that contain a C=C bond comprising of a pi bond and a sigma bond
-the pi bond holds the atom in position by restricting the rotation around the double bond

32
Q

What is a pi bond?

A

-a sideways overlap of adjacent p-orbitals above and below the bonding C atoms
-they can only be made after a sigma bond has been formed

33
Q

What is the bond angle and shape of an alkene?

A

-each bond angle repels by the same amount forming bond angles of 120 degrees resulting in a trigonal planar shape

34
Q

Define an electrophile?

A

An electron pair acceptor
-e.g. positive ions and molecules with a positive region of charge

35
Q

What is the reactivity of alkenes?

A

-alkenes are more reactive than alkanes
-as pi bonds have a lower bond enthalpy than sigma bonds so they are weaker, meaning in an alkene chemical reaction the pi bond will break first and react leaving a sigma bond between the 2 carbon atoms

-the double bond is an area of high electron density that will attract electrophiles

36
Q

What is hydrogenation and what are the conditions?

A

-an addition reaction where hydrogen is added across the C=C bond

-CONDITIONS -a temperature of 150 degrees Celsius, a nickel catalyst
-gaseous hydrogen and an alkene are mixed then passed over the catalyst in a reaction chamber
-this saturates the alkene and an alkane is produced

37
Q

What is halogenation?

A

-an addition reaction, where a halogen is added across the C=C bond- the alkene becomes saturated and a dihaloalkane is produced

38
Q

What can halogenation be used for?

A

-this reaction can be used to test for saturation
-when bromine or iodine solution is mixed with a saturated compound (an alkane) no reaction occurs
-however when bromine is added to an unsaturated compound (an alkene) decolorisation happens as an addition reaction occurs

39
Q

What is a hydration reaction?

A

-an addition reaction between a gaseous alkene and steam-used in industry to make alcohols

CONDITIONS- high temperatures (300 degrees Celsius), high pressure (65atm) and a phosphoric acid (H3PO4) catalyst

40
Q

What is the addition of hydrogen halides?

A

-an addition reaction in which a hydrogen halide is added across the C=C bond
-this produces a haloalkane
-hydrogen halides e.g. HCl , HBr and HI are gases at room temperature , these reactants are bubbled through the alkene to cause a reaction

41
Q

How can Markownikoff’s rule be used to predict the product when a hydrogen halide is added to an unsymmetrical alkene?

A

-it states that when H-X is added to an unsymmetrical alkene , the hydrogen becomes attached to the carbon with the most hydrogen atoms to start with
-because carbocations that have an alkyl group attached are more stable than those with hydrogen atoms attached

42
Q

What happens during a polymerisation reaction?

A

-monomers have their pi bond broken
-the electrons from each pi bond make a sigma bond with a neighbouring carbon atom on a different monomer
-this connects the monomers chemically generating a saturated polymer with long carbon chains

43
Q

What are the benefits of cheap oil-derived plastics counteracted with the problems for the environment of landfill?

A

BENEFITS: -they have many uses -clothing, materials in cars
-they are very stable
PROBLEMS:-due to the anaerobic conditions and lack of water in the large holes of landfill, the rate of decomposition is slow and many plastics are non-biodegradable
-if the waste does not break down it becomes a risk to wildlife

44
Q

What are the benefits to sustainability by processing waste polymers by combustion?

A

-the chemical energy that is made can be used to drive turbines and generate electricity
-however this combustion releases carbon dioxide which is a greenhouse gas it can also release other polluting gases
-these gases can be removed by using gas scrubbers, where a base like CaO neutralises acidic gas

45
Q

What are the benefits for sustainability by processing waste polymers by using them as organic feedstock?

A

-after waste plastics have been sorted into different types , a series of chemical reactions can be used to break plastic polymers up into small organic molecules
-this allows the recovered chemical to be used in other industrial reactions e.g. the production of plastics and other organic chemicals

46
Q

What are the benefits to the environment of development of biodegradable and photodegradable polymers?

A

-reducing the dependency on finite resources
-alleviating problems from disposal of persistent plastic waste

47
Q

What are biodegradable polymers?

A

-when a polymer like plant starch is mixed with an addition polymer
-these biodegradable polymers are affected by the action of microorganisms and environmental conditions , leading to decomposition

48
Q

What is a bioplastic?

A

A material made from a renewable source that is biodegradable

49
Q

What are photodegradable polymers?

A

-plastics that break down using energy with wavelengths similar to light
-they are either addition polymers with bonds within their structure that are weakened by absorption of light or they have an additive that is affected by light , which then weakens the bonds in the polymer
-once the polymer has been exposed to light it begins to break down and it is not possible to slow down the process

50
Q

What is a disadvantage of photodegradable polymers?

A

-photodegradable plastics in landfill may not be exposed to sufficient light to degrade

Chemistry Alevel OCR (9 decks)

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