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1 1 1 AAAAAAA A A A ALevel Chemistry Me > Module 2 Revision > Flashcards

Module 2 Revision Flashcards

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1
Q

Homolytic fission

A

Homolytic fission if a covalent bond is where each one of thr bonded stoms take ONE electron each from thr shared pair if electrons, leaving two radicals

As they the same = radical

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2
Q

Radical

A

A highly reactive species containing an unpaired electron

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3
Q

Heterolhtic fission

A

Is when one of the atoms bonded takes all the electroms from the bonded pair, leaving a positvely and negatively cahrged ion

As different = heteri

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4
Q

Homologous series

A

A family if organic compunds with that share similar chemical characettisics
and each foklow the same general forumla,
where each successive member differs by a ch2 group

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5
Q

How are alkanes joined

What is a covalent bond
Sigma bond

A

By single covalent bonds known as sigma bonds

Covalent bonds result due to the overlap of two orbitals
- a sigma bind is due ti the head on overlap of any two orbitals , where the electrondensity is found along the line connecting the two nuclei

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6
Q

What increases / decreaes boiling point of alakens

A

1) increase chain lentgj= increase

2) increase branch = decrease

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7
Q

Why increase chain length increase boiling point

A
  • increase the chain lentgh yiu increase the surface contact area between moleculed (chaind
  • this means there will be more london forced made between and thus
  • as more energy needed to ivercome these binds = higher boiling ooijt
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8
Q

How branching decrease boiling if alkanes

A
  • increase of branching
  • reduces surface contact area beween chains = means less london forced
  • reduces how close chains can ger together = which means weaker london forces
  • which means less energy needed to overcome and thus less boiling oiunt
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9
Q

Why alkane good for combustion

A
  • burn in plentiful oxygen without releasing toxins
  • readily sviaoaboem
  • easy to transport
  • reauire less oxygen
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10
Q

In omplete combustion productd

A

C + h20
Co + h20
C+co+h20

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11
Q

What RAY OF RADIATION IS NEEDED TO MAKE A HAKOGEN HOMOLYTICALLT FISS

A

Uv raysss

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12
Q

Radical substition of methane and chkorine + conditiosn

A

1) initiation = uv light
- Cl2–> Cl- + Cl-
2) propagation
Ch4 + Cl- —> Ch3 -+ HCl
CH3- + Cl2 —> Ch3Cl + Cl -

Then termination , the reaction continues untik two radicals react

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13
Q

What are limitstions of using radical substition to make your product (2)

A

1) further substition means your product msy go again and lose a hydrogen and make a different product
2) you may get different monosubstituted isomers (structural) if chain lnegth long. This woill lead to even more possibilities if it gets further substitiued . This gives mixture of incirredt lroduct

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14
Q

Unstaurated hydroxarbon

A

A hydrocarbin that has atleast one c=c , or triple bond

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15
Q

What is the nature of bonds in an alkene

A

Alkenes contain both a sigma and a pi bond
- a sigma bond resukts from the headon overlap between two orbitals
- a pi bond results from the SIDEON overlap between two p orbitals, where the electron density is found above and below the line connectinf nuclei
As a result the pi bond having this density prevents the alkene from rotational movement , as you would have to break this bond first = gives rise ti ex idomerism as they are fixed in space

Shape is 120°
Three bindinf grouos, repel as much as possible no lone paids so 120°

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16
Q

What is stereoisomerism

A

Where molecules have same steuctural and molecular formula but different areangment of atomd in dosde

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17
Q

What are conditions needed for e/z isomerism?

Why

A
  • a C=C double bond
  • different groups attached to each carbon atom of the double bond

E/ z isomerism only works because electron density above and belwo line means the atoks are fixed in space as they cant rotate. As a result fixed in space

  • also needs two different groups to diffentiate
  • just because not e/z doesnt mean not alkene!
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18
Q

What about ruling for cis trans isomerism ?

A

Here this is a SPECIAL CASE OF EZ
- so still need double bond
- and different groups
- BUT
ONE ATOM BONDED TO EACH CARBON MUST BE HYDROGEN
- here if bith same thrn cis if across then trans

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19
Q

How to assign priority again

A

MAKE SURE TI CHECK ATOMIC NUMBER NOT MASS!

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20
Q

Why are alkens more reactive then alkanes? (2)

A

The fact that they have two bonds, a sigma and pi means greater electron density , as nit only is it along the line connecting the two nuclei but above and below

1) As a result more electron density = means more of a chance of an electron being found in that area = ELECTRONS ARE MORE EXPOSED IN ALKENES AND HIGHER CHANCE OF FINDING then alkanes.
2) the bond enthalpy of a doubke bind is less than a sigma

Therefore the nature of pi bind means alkenes undergo reactions more easilly, also because the doubke bind breaks easier to

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21
Q

4 reactions of alkenes + conditions?

A

1) hydrogenAtion
- Ni catalyst + 423 k
2) hydration
- steam (g) + conc acid catalyst like h2so4

3) halognation full halogen
- electrophilic addition
- room temp

4) halogenation with hydrogen halide
- electrophilic substiton but two PRODUCTS MADE THIS TIME
- can be hydrochlric acid or hydrobromic acid too!

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22
Q

Difference between margarine and butter

A
  • butter is more firm due ti having more majority staurated chains
  • margarine not as more prorpition unstaurated, which causes kink and lowers melting poijt
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23
Q

How ti use halognation ti tret for staurwtion?

A

Bromine water is orange yet will become decolourised if added to alkene as unstartuated and can dd

Any compound containing this will decolourise bromine water

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24
Q

What is electrophiles

A

Electriphiles are species that accept a pair of electrons , snd thus are usually positibe or partial positve charge

They are attracted to the high electron density region of the alkene

2) a dipole is made whetehr due to electronegativity differences are just an induced dipole oushing electrons away to the highly electron density regioj
2) the electron lair in thr pi bond breaks
3) a bond is mase between the carbon and the hydrogen atom
4) hydrogen bromine arom breaks homolyticallt to form an ion snd a carbocation
5) thid is attracted to the positive carbocation and another vond here is made

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25
Q

How induced dipole

A

Bromine approaches alkene the pi bond electrojs intercat causign induced poalriswtion of thr bromine making one + snd one nebsttige

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26
Q

What is markownikoffs rule for major products and what is axfuak rule

A

Markownikoffs ruke suggests the hydrogen of a hydrogen halide attaches itsked fo the carbon with the MOST hydrogens already attached (making other carbocation)

However really the carbocation forms to the side it will be kost stable in, based on how many ALKYL GROUPS

  • more alkyl grouos =more electrons donated and pushed towards positve charge which helps spread it out
  • so more alkyl = more charge sprewd out and more stagke
  • thus tertiary more then normal
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27
Q

Why aee teritiaey mor estabel then normal

A
  • more alkyl grouos =more electrons donated and pushed towards positve charge which helps spread it out
  • so more alkyl = more charge sprewd out and more stagke
  • thus tertiary more then normal
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28
Q

Addition polymerisationn

What cindition

A

Open brakct + n

1) high temp and pressure

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29
Q

What is pvc polychloroethane used for

A

Pipes, films , ductd and profiels, i sukatiok, bottles etc

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30
Q

Why polymers used for storing food but what same property means its hard to dispose?

A

Lack of resctivity mesns perfect for storing foods

However we barely reacts it is non biodegradeable snd stays around for ages

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31
Q

How can we reduce malunf ofmpolyer,s

A
  • Recyling + feedstock recycling
  • using waste polymers as fuel
  • moving to biodegradeable and photodegradeable polymers
32
Q

How are polymer recycke

What is feedstock recyeling and what sdvantages

A
  • sorted , as if not it csnt be recycled
  • chopped into flakes washed dried melted wnd resused

Feedstock recyling
- is chemical and thermal process of extracting monomers , gases oil from polymers, and doesnt need to be sorted. This way materials can be used as raw materials again

33
Q

Why pvc dangerous to recyle

A

Its got chlroije and went burn as dangerous , also dumping into landfills is not good either

Now new tech used to deal with it

34
Q

How can waste polymers act as a fuels

A

They come from petroleum so have high energy

- incinerated produce heat, makes steam move turbine = electricity

35
Q

What are bioplastics

A

Those produced from starch cellulose plant oils offer a renwabke and sustainalbe alternwtive ti crude oil, nit only protects enviroment but saves limited oil reserves

36
Q

Biodegradeable polymers

How broken down

What do compostsble ones do and what are retail uses

A

Broken down by microorganisms into co2 water etc

  • compostsble ones degrade and LEAVE NO VISIBLE OR TOXIC RESIDUES
  • supermarket bags can be like this so they compost with the biological waste
37
Q

What are photodegrwdable polymers?

A
  • when plant based not available photo is used as this is using light to initiate degradation rpocess
38
Q

Alkanes vs alcohols of same carbon lentgh properties?

A

At same carbon , alcohols will be

  • less volatile (boiling)
  • higher MELTING point
  • more soluble

This is because

  • alkanes have little electonegagivity difference = not polar so stringest bond is weak intermolecular
  • howevwr alcohols have a Oh group which has a difference and thus polar. Moreover has a HYDROGEN BOND
  • thus you will have to overcome hydrogen bonds aswell as intermolecular so melting point of alchol increase. Harder to boil = volatility decreases
  • solubility increased due to alcohols being able to mske a hydrogen bond with water , and energy made here is way more than weak intermolecular bonds make when a non hydrogen bond made, so this energy can overcome already weak intermolecular bonds and thus be soluble in water
39
Q

However what changes a carbon lentgh increases between alchols and alkanes

Increase Oh?

A
  • as chain lentgh increases, the infludence of thr zOh group is not as noticeable , and solubility boiling melting eveythung becomes similar to alaknes

However increasing OH = increase everything

40
Q

Alchol reactions

A

1) oxidation primary to aldehyde
Alcohol + 1[O] —> (k2cr2o7/h2so4) becomes aldehyde + one water
Distil + gentle heat
Colour orange ti green of cr2o7 2- ions to cr3+ green

2) oxdiation primary to carboxylic acid
Alcohol + 2[O] —> (k2cr2o7/h2so4) becomes carboxylic acid + 1 water
Strong heat + reflux + excess dichromate

Orange to green

3) oxidation secondary to ketone
Sec alcohol + [O] —> (k2cr2o7/h2so4) becomes ketone + one water
Orange ti green
Reflux + excess + strong heat

4) dehydration alchohol to alkene
Alcohol + conc acid catalyst and reflux gives h20

5) alcohol substitution (nucleophilic) with sodium halide
Sodium halide + h2so4 reflux

Makes hydrogen halide in vitu
Which readts wirh alcohol to give you haloalkane and a water

41
Q

What makes haloalkanes reactive (why nucleophiles attracted)

A

This is because there will be a dipole formed due to electronagyovoty differences between the halogen and the carbon , making it polar

As a result a nucleophile can be attracted and donate their electrons causing reactions

42
Q

What is a mucloephile

A

A species that donates a pair of electrons

Here if they have electrons = they negative, so ions OR lone pair
= oh nh3 h20 anything

  • reason dipole ones with h not because they regularly make ions anyways ( I think)
43
Q

What is process fo making haloalkane back into alcohol

A

Hydrolysis with something like MAOH which involves nucleophilic substation

44
Q

What happens in nucleophilic substitution

A

1) the nucleophile approaches partially positive carbon ( due to being attracted ) OPPOSITE to the halogen ( this is to minimise repulsion between both negative charges )
2) a covalent bond is made as the nucleophile donates its electrons to the carbon , at the same time the carbon halogen bond breaks heterolytically
3) this forms an ion and an Alcohol

45
Q

What does hydrolysis require

A

Reflux to soles and source of OH = NaOH

46
Q

Rate of hydrolysis

A

Depends on strength of covalent bond , weaker it is , the higher the rate of hydrolysis

Here the lower you go = the weaker the bond = less energy needed to break it so rate increases

47
Q 
How to do test to show rate of hydrolysis  (theory)
Why ethanol
Why reagent (2)
A

You can use AQUEOUS silver nitrate test to test for halogen ions produced
- and here the OH is provided by the aqueous ,
however the silver nitrate and the haloalkane are insoluble in water so an ETHANOL SOLVENT USED

48
Q

How to actually do the rate of hydrolysis experiment then?

A

1) heat up some ethanol with some haloalkane in different test tubes
2) at same time heat up some silver nitrate in a separate
- allow all to come to same temp

3) then at a certain time add the silver nitrate and start a stop clock and measure the time taken for precipitate to form and do one / t

Expected = cl takes the longest to form, i takes quickest so yellow quick milk slow

49
Q

What are organohalogens

A

Those that have Atleast one halogen joined to a carbon chain

50
Q

What happens to ozone in the stratosphere (how normally made )

How do human activity cause this to stop

A

Oxygen molecules homolytically break to give radicals and this REVERISBLY REACTS WITH OXYGEN TO MAKE OZONE

however the CFC and human activity breaks this equilibrium speeding up break down of ozone

51
Q

What happens ro radiaitoj coming from the sun (how does global warming come about + role of ozone)

A

1) some is absorbed by ozone straight away
2) some passes to the earth surface which just gets absorbed
3) some is re emitted (still INFRA RED JUST LONGER WAVELENGTH)
4) then this is absorbed by greenhouse gases in the atmosphere (co2, water , methane) as its naturak frequency and re emits , heating up earth

52
Q

What are CFCs and whatbeere they used for (2)

Why were CFCs used before, and for aerosols

A

Chloroflurorocarbons , used before to make PROPELLANTS and REFRIGERANTS (to propell and keep cool)

Used before because very stable due to carbon halogen bond

53
Q

So why cfc bad

Why are chlroine radicals made

A

Cfc bad because they only stable until they reach the earthe stratosphere, where they can break down due to UV radiation,
As the chlorine carbon bond weakest , it breaks first so CHLORINE RADICAKS MADE

54
Q

Show how a chlorine radical made and how it goes after to break down o3

Where did o radical come from again!

A

CF2Cl2–> CF2Cl- + Cl- (initiation with UV radiation)

Then Cl- + O3 —> o2 ClO-
ClO- + O- —> Cl- + O2
Overall O3–> O2 + O
Chlorine radical regenerated (catakyst) which can further do the chain causijg extreme breakeage !

Came from o2 breaking to make o radicals which forms part of equilibrium to make o3

55
Q

What other radical can cause depeletion of oxone and how made, plus full reaction

HOW IS IT MADE !!!!

A

Nitrogen oxide radicals that form from LIGHTINING STRIKES AND ALSO AIRCRAFT TRAVEL

NO- + O3–> NO2- +O2
NO2- + O- —> NO- + O2
Again O3 + O —> 2O2

56
Q

Apparatus remember

A

Round bottom flask or pear shaped flask

  • receiver
  • STILL HEAD (which combines a flask with condenser and thermeometer pocket (screw tap)
  • condenser
57
Q

Hoe to do reflux apparatus

What to use to make more safe , what to make shre not to do and anti bump?

A
  • clamp a flask , attach a source if heat undernath (HEATING MANTLE MORE SAFE)
  • now add mixture into flask With ANTI BUMPING GRANULES
  • then add condenser on , ensured it is GREASED
  • finally dont close to the top to ensure no pressure build up
  • RUN WATER, remember water always goes in lowest fir (2 reasons)

Heat

58
Q

So why need anti bumping

A

Need jt because contetns boil SMOOTHLY, or else large bubbles form at the bottom of the liquid and can make glassware VIBRATE OR JUMP VIOLENTLY

59
Q

Why grease

A

Ensuee grease joins so a tight fit established

60
Q

Why water in at bottom

A

Nit knyl does it ensure a more efficient cooling , but it esnures there are no gaps going against gravity

61
Q

How to set up distillation

A
  • clamp flask to clamp , add reaction mixture in and antibumoing granules
  • then grease joins and add still head in , connect this to ckndenser and thermometer pocket (screw tap)
  • connect second part if condenser to another clamp, and connect to a greased reciever , putting a collection beaker underneath
  • attach water at bottom, connect water out ti doke weight attach thememeimer

Heat

62
Q

Distillation vs reflux?

A

Distillation allows you to separate a less volatile substance by boiling and findijg it a tempertaure from other higher boiling point impurities
Whereas reflux ensures a liquid to be continouslt boiled whilst reaction takes place, withiut loss of voltalile substance

63
Q

How to separate and clean organic product formed thst maybe with an aqueos layer?

A

1) identify the aqeuos layer , do this by adding water and the one that increases is the aqeuos
1) separate using separating funnel, (invert to mix and react, let out oressure, couple times) then ket the aqeuous go and collect organic
2) if acid used before need to kake this go so add SODIUM CARBONATE , allow react remove pressure and separate . Do this three times
- then wash with water, this will remove the salt formed hopefully

3) now jeed to dry the remainder water, so add to bottole and SODIUM SUKFSTE and swirl, and keep sdding until solid NO LONGER LUMPS TOGETHER , but make sure not add tok much or lose product
- now decant liquid by just pouring it away

4) FINALLT NEED TO REDISTILL TO ENSURE ANY LAST IMPURITY (such as some water, some drying agent anything can keave.. collect product ONLY AT BOILING TEMP YOU NEED

64
Q

Summary of wash and clean purifying

A

1) add to separating funnel, add water to see aqeuos, then remove bottom layer and separate,
2) now add sodium aqeuos sodium carbinate to remove acid, releas epressure and separate, do three times
- add water wash to remove salt formed
3) now need to dry so add anhdyrous sodium sulfate until no longer clump, decant
4) finally redistill to remvoe any ladt impurity snd collect at expected range

65
Q

What happens in mass spectrometer?

What about fragments and what is detcted

A

Organic ompound loses an electron to form positbe ion which is just the molecular ion, one clearly kn right (furthest is ine up because of carbon 13 isotope that is present in 1.1% carbon) and one on righ id = to moclular kass

Some molecukar ions can fragment to make other frwgment ions and radicals, but ONLY FRAGMENT IONS DETECTED

66
Q

Covalent bonds vibrating how in 2 ways

What does amount it virbstes depend on

A

Vibrwte naturally but the ABSORBTION OF IR makes them vibrwte even more
One is a stretch in and out so distance of line increase
One is abend which resuktd in CHANGE IN BOND ANGLE

The amount it vibrates depends on mass of atoms (heavier = more vibrate)
And strentgh if bonds (stringer = more vibrate fatser)

67
Q

What freauency can a bond absorb

A

Only the same frequcny as the natural frequcny

As frequcny values so large we use wavenumber, 1/ wavlentgj which is propeotionwl to the frequcny

68
Q

,how does ir spectromerty work

Transmitted and what! How do graoh show low areas for transmittance

A

Samoke oladed in soectormeter
2; beam of radiation 2- 4 k wavenumber passed
3) molecule will absrob soke of IR frequencies ifnit matched its natural frequency
- the emerging wave dpis detected to see what have been absorbed and not
3( based oj this the IR spectrometer and a computer cah produce what has been transmitted , low areas are thus areas WHICH ARE ABSORBED

69
Q

What is fingerprint region

A

Unique peaks that can identify molecule, however diffucukt to see manually

70
Q

Common ways ti distingusih

A

Everything will always have charcterisitc c-h bind, butbthis soemtimes overlap with alcohol

2) carbox will be disticnt if it meets its own
3) alcohol distinct if it meets its own
4) but jetone or aldehyde can only he told by the 1630- 820 oje , around 1700 alone, if this is paired with carbox = carbix, if not its one or the other

71
Q

App,ications of ir

Alcohol, what is detected snd how can amount if slcohol be detected

A

To identify pollutwnte by IR fingerprente , where remote sensors analyse ir of vehicle emissiojsnto monitor

Breatkysere , where characteristic ethanol bond is detected and MORE ABSORBED MEANS MORE WAS ORESENT , and a database can show this

72
Q

What twkes priority for naming the kast one

A

Last one = carboxykic acid
Then aldehyde / ketone
Alcohol
Etc

Then alphabetical order and lowest number whatever

73
Q

What happens to light from sun reaching earth

Why ozone needed

A

1) ozone needed because a lot of ozone absorbs harmful radiation from sun

2) a lot is transferred to the earth surface and absorbed
- some is then reemiited

74
Q

Common ir transmittsnce

A

If it’s a double bond for alkeens transmittsnce slightly lower compared to insane transmittsnce by aldehydes and ketones

Now this shows up with the carboxylic one too , basically if big leak hint it is aldehyde ketone or csbrodn

75
Q

How to show in tests for evidence

A

Need to show both wave number and type of bond , not in words

1 1 1 AAAAAAA A A A ALevel Chemistry Me (43 decks)

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