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DIY chem > Mod 4 > Flashcards

Mod 4 Flashcards

1
Q

What is a hydrocarbon

A

. Compound consist of carbon and hydrogen atoms only

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2
Q

What is a saturated compound

A

. Has only single bonds

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3
Q

. What is an unsaturated compound

A

. Contains at least one carbon to carbon multiple bond

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4
Q

What is an aliphatic compound

A

. Where the carbon atoms are joined together to form a straight chain branched or unbranched

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5
Q

What is an alicyclic compound

A

. Where the carbon atoms are joined together in a ring structure

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6
Q

What is an aromatic compound

A

. Compound containing a benzene ring

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7
Q

What is a homologous series

A

. Series of organic compounds with the same functional groups but with each successive member different by CH2

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8
Q

What is a functional group

A

. Part of the organic molecule or a group of atoms responsible for its chemical reactions

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9
Q

What is an alkane

A

. Homologous series with the general formula CNH2N +2

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10
Q

What is a general formula

A

. Simplest algebraic formula of a member of a homologous series

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11
Q

What are the three types of structural isomerism

A

. Chain isomerism - hydrocarbons can be branched or unbranched
. Positional isomerism - functional group can be a different position
. Functional group isomerism - functional group can be different all together

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12
Q

Aldehyde, ketone, ester, amine

A

. O=C-H, al e.g. propanal
. O=C, one e.g. propanone
. C-O-C, oate, e.g. methyl propanoate
. C-N-Hx2, amine, propylamine

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13
Q

What are the properties of alkanes

A

. Nonpolar molecules as there is no significant difference between electronegativity of carbon and hydrogen
. Based on carbon carbon covalent bonds
. Very unreactive to a broad range of chemicals
. Are used extensively as fuels

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14
Q

What is the structure and bonding around c atom in alkanes

A

. There are 4 bonding present 0 lone pairs are in each carbon atom
. All electron pairs repel
. molecule forms a tetrahedral shape around each carbon atom
. Bond angles around each carbon will be 109.5°

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15
Q

What is a sigma bond

A

. And on end overlap of bonding orbitals directly between atoms (in all single bonds)

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16
Q

What is bond rotation in an alkane

A

. All bonds in an alkane can rotate

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17
Q

Boiling in melting points relating to hydrocarbons

A

. Longer chain equals higher melting and boiling points due to more points of surface contact between molecules so strength of induced dipole dipole interaction increases between molecules which requires more energy to overcome
. branched isomers have lower boiling points due to less points of surface contact so weaker induced dipole dipole interaction between molecules that require less energy to overcome

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18
Q

What is combustion and Write equation for the combustion of alkanes

A

. Complete combustion-burning of a substance in excess supply of oxygen
. I.e CH4 + 2O2 —> CO2 + 2H2O
. Incomplete combustion-burning of a substance in limited supply of oxygen
. I.e. CH4 + 1.5O2 —> CO + 2H2O
. I.e. CH4 + O2 —> C + 2H2O

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19
Q

What kind of hydrocarbons are more efficient as fuels

A

. Branched chains are preferred to be used as fuels as they have more efficient combustion

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20
Q

What is a radical

A

. A highly reactive species with an unpaired electron 

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21
Q

What are the types of bond fission

A

. Homolytic fission - covalent bonds break and one electron goes to each atom forming to radicals
. Heterolytic fission - covalent bond breaks and both electrons go to the same atom form into ions

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22
Q

Draw a mechanism for free radical substitution including the reaction conditions

A

. Reaction condition-UV and high-temperature
. Initiation Cl2 —> ^UV Cl. +Cl.
. Propagation Cl. + CH4 —> .CH3 + HCL, .CH3 + Cl2 —> CH3Cl +Cl.
. Termination .CH3 + Cl. —> CH3Cl, .CH3 + CH3 —> CH3CH3, Cl. + Cl. —> Cl2 

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23
Q

What are the problems of free radical substitution

A

. Multi substitution occurs-overcome this by using excess alkane
. Mixtures of products form-they are unwanted bi products
. isomers-substitution occurs anywhere along the chain forming isomers

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24
Q

What is ozone and describe natural formation of O3

A

. Ozone found in the stratosphere
. I ozone absorbs UV radiation so UV at Earth surface is reduced
. O2.—>^UV O+O
. O2 + O —> O3

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25
Q

What are chlorofluorocarbons CFCs

A

. Contain chlorine fluorine and carbon all – all hydrogen is replaced
. They are stable, volatile, non-flammable and non-toxic
. Used in the past in aerosol cans, dry cleaning, air-conditioning, and fridges
. Not use anymore cause they destroy the ozone layer

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26
Q

What is the reaction occurring when CFC is enter the upper atmosphere

A

. Initiation Cf2Cl —>^UV CF2Cl. +Cl.
. Propagation Cl. + O3 —> O2 + ClO., ClO. + O —> O2 + Cl.
. Overall O3 + O —> 2O2

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27
Q

What is nitrogen oxides effect on the upper atmosphere and equation

A

. NO. Free radicals for nitrogen oxides, and destroy the ozone two
. NOI produced by thunderstorms, cart/aircraft engines
. Similar reaction as chlorine radicals
. NO. + O3 —> O2 + NO2
. NO2 + O —> O2 + NO.
. OVERALL O3 + O —> 2O2

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28
Q

What are the alternatives to CFCs

A

. Hydrochlorofluorocarbons (HCFC) and hydrofluorocarbons (HFCs) of being used until saferalternatives are developed
. HCFC is a broken down in the atmosphere more quickly
. HFC is broken down the atmosphere too they don’t contain chlorine and so don’t affect the ozone layer
. HCFCs and HFC are greenhouse gases
. Other alternatives include aerosols with pump spray/nitrogen components, fridges freezers using ammonia as the coolant gas, CO2 is used to make expanded polymers

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29
Q

what are the properties of alkenes?

A

. general formula CnH2n
. unsaturated hydrocarbons with at least one c=c functional group
. alkenes are more reactive than alkanes undergoing addition reactions

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30
Q

whatare sigma and pi bonds

A

. sigma bonds - end on ned overlap of orbitals directly between atoms (single bonds)
. Pi bonds- sideways overlap of P orbitals to give a Pi bond directly above and below (double bonds)

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31
Q

how many Pi and sigma bonds are present in double and triple bonds?

A

. double bond contains 1 sigma and 1 Pi
. triple bond contains 1 sigma and 2 Pi

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32
Q

what is the shape and rotation around a c atom in an alkene?

A

. trigonal planar shape around each atom in c=c bond
. no rotation around c=c bond as p orbitals must stay in the same position to overlap and form a Pi bond
. any c-c bonds will still rotate

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33
Q

what is stereoisomerism

A

. have the same structural formula but a different arrangement of atoms in space

34
Q

what is the difference between E/Z isomerism

A

. Z is when both groups are on the same side _/
. E is when both groups are at either side

35
Q

what is the Cahn-ingold-prelog priority rules

A

. it assigns priority to different atoms to name isomers
. atom with higher atomic number on each carbon is given higher priority
. in e isomers tehyll be positioned on opposite sides to eachother
. in z isomers theyll both be on the same side

36
Q

what is the reactivity of alkenes?

A

. Pi bonds are weaker than sigma bonds
. Pi bonds break and electrons can be donated to form a bond
. invlved in reactios called addition reactions
. addition reactions have 100% economy

37
Q

how do you synthesise a dihaloalkane?

A

. alkenes react with halogens to produce dihaloalkanes
. reaction conditions 20 degrees
. is halogenation

38
Q

how do you synthesise a haloalkane?

A

. alkenes react with hydrogen halides to produce haloalkanes
. reaction conditions 20 degrees
. is an example of halogenation

39
Q

how do you test for alkenes/ saturation?

A

. add bromine water solution and shake
. contains double bond - orange to colourless
. contains no double bond - no visible change
. bromine is added across the double bond

40
Q

how do you syntehsise alkanes?

A

. alkanes react with hydrogen gas to produce alkanes
. reaction conditions Ni catalyst and 150 degrees
. is an example of hydrogenation

41
Q

how do you synthesise alcohols

A

. alkenes react with steam to produce alcohols
. reaction conditions H3PO4 60-70atm and 300 degrees
. example of hydration

42
Q

what happens to unsymmetrical alkenes in reactions?

A

. they can form isomers
. one of these isomers will be the most stable, this will be the major product and any less stable products wil be minor products

43
Q

what determines carbocation stability?

A

. if its determined to multiple alkyl group, can be primary, secondary, or tertiary

44
Q

what is an addition polymer?

A

. monomers are single repeating units
. polymers ar emade up of long repeating units of monomers

45
Q

what is the reactivity of polymers?

A

. alkenes are unsaturated compunds
. polymers are saturated compounds
. polymers are chemically inert and not biodegradable

46
Q

what casues polymer waste?

A

. polymers are unreactive so are not biodegradable
. this makes them long lasting and reusable but difficukt to dispose of

47
Q

explain burying waste plastic?

A

. done when plastic is too difficult to separate
. not in sufficient quantities to make separation financially worthwhile
. too difficult technically to recycle

48
Q

explain recycling plastics?

A

. we can sort plastics into different types
. polypropene can be melted and remoulded
. others can be cracked into monomers which can be used as organic feedstock to make more plastics/ chemicals
. overall process involves sorting and processing

49
Q

explain burning waste plastics

A

. waste plastics can be burnt and the heat can be used to generte electricity
. toxic gases can be released
. passing through scrubbers containing NaHCO3 neutralises and removes the HCL

50
Q

explain biodegradable/ photodegradable polymers

A

. made from materials such as starch and the hydrocarbon isopropene
. renewable raw materials wil not run out
. carbon neutral for plant based polymers
. plant based polymers save energy

51
Q

wht are the properties of haloalkanes

A

. they are polar molecules due to the polar carbon-halogen bond
. halogens can be represented by an X symbol

52
Q

polarity of haloalkanes

A

.polar molecule - halogen atom is more electronegative than the carbon atom thus withdraws eletron density from the carbon chlorine bond
. partially positive carbon can react with nucleophiles

53
Q

what is a nucleophile?

A

. electron pair donor
. said to be a region of high electron density
. curly arrows represent movement of an electron pair

54
Q

what is a substitution rection?

A

. involves swapping of nucleophiles and halogen atoms
. atom economy always less than 100%

55
Q

what affects the rate of hydrolysis?

A

. depends on bond enthalpy of the carbon halogen bond
. weaker bonds break more easily and so reaact faster

56
Q

what are the bond entahlpies of carbon halogen bonds?

A

. C-F - 467 KJmol
. C-Cl - 346 KJmol
. C-Br - 290 KJmol
. C-I - 228 KJmol

57
Q

how can you compare the rate sof hydrolysis using H2O?

A

. add silver nitrate solution to the mixture
. silver ions react with halides as soon as they form, silver halide precipitate forms
. reaction is known as aqeous hydrolysis
. RX + H2O –> ROH + HX

58
Q

what re the properties of alcohols?

A

. alcohols are polar molecules
. due to the electronegative hydroxyl groups which pull electrons in the C-OH bond away from the carbon atom

59
Q

what are the boiling points of alcohols?

A

. alcohols have higher boiling points compared to alkanes
. alcohols are less volatile than alkanes of similar carbon atoms

60
Q

explain hydrogen bonding in alcohols

A

. alcohols have hydrogen bonding between molecules
. alkanes have induced dipole dipole interactions between molecules
. hydrogen bonding is stronger and requires more nergy to overcome

61
Q

explain the solubility of alcohols

A

. alcohols with short carbon chains are soluble in water
. alcohols and water molecules make hydrogen bonds with eachother
. alcohols make neutral solutions
. if there are more OH groups, there are more hydrogen bonds so the alcohol will be more soluble

62
Q

link alcohol solubility to chain length

A

. the greater the carbon chain length the less soluble in water
. there are stronger induced dipole dipole interactions in longer carbon chains
. which break up hydrogen bonds between molecules

63
Q

explain combustion reactions with alcohols

A

. alcohols can be oxidised by combustion
. they are good fuels with high enthalpies of combustion so produce a lot of energy per mole of alcohol burnt
. theyre added to petrol mixtures to prevent incoplete combustion as they contain an internal supply of oxygen in OH group

64
Q

explain synthesis reactions of haloalkanes from alcohols

A

. synthesis of haloalkanes from alcohols
. alcohols will react with compunds that contain halides in a substitution reaction
. reaction conditions and reagents: NaBr H2SO4 and 20 degrees

65
Q

explain elimination reactions in alcohols

A

. synthesis of alkenes from alcohols
. conditions and reagents: H2SO4 or H3PO4 and heat
. example of dehydration

66
Q

explain oxidation reactions in primary alcohols

A

. heating a primary alcohol with potassium dichromate(VI) K2Cr2O7 solution and H2SO4 with distillation apparatus produces an aldehyde
. heating with excess oxidising agent and h2so4 under reflux produces a carboxylic acid

67
Q

what happens to alcohols in oxidation reactions?

A

. heating an aldehyde with K2Cr2O7 and H2SO4 with reflux apparatus produces a carboxyllic acid and no water

68
Q

What happens to secondary alcohols in oxidation reactions

A

. heating a secondary alcohol with excess oxidising agent and H2SO4 under reflux apparatus produces a ketone

69
Q

what happens in oxidation of tertiary alcohols

A

. cannot be oxidised so no reaction

70
Q

how do you test for alcohols?

A

. tertiary alcohols dont react with acidified K2Cr2O7
. this means they can be used to test between primary and secondary alcohols against tertiary alcohols
. add few drops of potassium dichromate (VI) and a few drops of concentrated H2SO4
. colour change from orange to green = primary and secondary alcohols
. no visible change in tertiary alcohols

71
Q

draw reflux and distillation apparatus

A

nuh uh

72
Q

when is distillation used?

A

. used to react substances and remove the product to prevent further reaction

73
Q

when is reflux used?

A

. used to react volatile substances together to prevent substances from escaping

74
Q

What is an electro file

A

Electron pair acceptor

75
Q

What is redistillation

A

. Used to purify
. Select the fraction having the boiling point of a pure compound
. Draw a distillation apparatus

76
Q

What is a Separating funnel and when is it used

A

. Products of a reaction of water is added to a separate Funnel whichis shaken and allowed to settle
.  less dense organic layer settles at the top
. Water soluble impurities dissolve in the lower aqueous layer
. Stop it he’s turned aqueous Layer is run off

77
Q

What is a vacuum filtration

A

. When solids are filtered under vacuum

78
Q

What is infrared spectroscopy

A

. Beam of infrared radiation passed through sample of chemical
. Bonds between different atoms absorb different frequencies of IR radiation
. IR radiation causes covalent bonds to vibrate more
. IR radiation that is not absorbed is detected by a detector

79
Q

Explain how infrared radiation affect global warming

A

. Greenhouse gases in troposphere absorb readmitted IR radiation from earth
. This is real mood in all directions including back to earth

80
Q

What are uses of IR spectroscopy

A

. Modern breathalysers use IR to look for presence of ethanol in breath by detecting OH bonds
. monitoring gases causing air pollution

81
Q

When is mass spectroscopy used

A

. Determine abundance of isotopes in an element
. Can monitor breathing of patients under anaesthetic
. Testing for drug use in athletes/horses
. Analysing molecules in space
. Testing for toxic chemicals that may have contaminated marine life

DIY chem (4 decks)

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