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a level chemistry year 13 > Exam Technique > Flashcards

Exam Technique Flashcards

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1
Q

Why does phenol react more readily with. Hlorined then benzene

3 main points

A

The lone pair from oh partially delocalised into the system of light bonds

This increases electron density

And so phenol can polarise chlorine more

In comparison to benzene

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2
Q

Why 2-4direcitn have mixture of products

A

SUBSTITUION AT DIFFRENT PLACES

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3
Q

How to do STRUCTURAL ISOMER QUESTIOSN

Say for c8H10

A

remember if you add something on the benzene you lose a hydrogen, use this to make sure hydrogen count is correct

Here you know benzne ring will take c6h6, but actually if you add a c then you lose a H, so you can put two Hs extra you thought not before , !!

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4
Q

Showing bro inaction with ohenol what to do?

A

SHOW THREE BEZNENES ON IT EVEN IF IT DINT MENTION

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5
Q

Remmeber when cyclohexene adds on bromine what it becomes

A

CYCLOHEXANE!

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6
Q

How to compare resistance of brominatioj what need to say

A

- cyclohexene electrons are loalcise dso greater electron density

-benzene electrons are delocalised ! (In a CONTINOUS system of pi bonds. Thus electron density is spread out )

  • phenol lone pair on O oh OH partially delocalised into pi system to increase electron density co pared to benzene

As cyclohexene and phenol have greater electron density compared to beznene, they can successfully induce a dipole (in whatever ) more / attract electrophile more

Thus addition happens more readily reduces resistance

So localised electrons vs delocalised benzene and partially delocalised

How this changes density

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7
Q

Okay fir makes what to say comparing reavtivitied between ebnende and Alkenes

A

PI ELEFTROMDNare delocalised for Beinen
And PI a electroms are local sided between 2 carbons in aleken

Thus between 2 carbons Alkenes age more electron density and thus can polarise bromine more and atgrvst the electrophiles

!!pi ELECTROMD

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8
Q

How ti de Sri be structure if benxne with diagram

EXTRA STUFF MAKE SURE INCLUDE

A

Show diagram either before and after to show pi bonds have overlapped or just draw rings to show

Then say benzene is planar ring 6 carbon 3 electrons et

Last electron sits in p orbialts 90 to plane

These OVERLAP to form a CONTINOUS ring of electron density ABIVE AND BELOW THE RING, forming a system of PI BONDS. Here the ELECTRONS ARE DELOCLAISED

4 things
Overlap
- forming electron density above and below
- forming system of pi bonds
- where electrons are said to be delocalised

2) HERE - ring is planar (got that)
- sigma bonds between cc and ch (got that
- BONDS ARE ALL EQUAL IN LENTGH
- and angles are 120° (as planar)

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9
Q

Extra things to mention in strufture of benzene

A

Bind angles are 120

And lentgh is the same everyhwere

And planar
And a,so sigma between others

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10
Q

Oh damn if they say suggest anither product likely to be formed in nitration of ohenol what you say

A

Lie 3 nitro

Or double substituier just something extrem

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11
Q

BEUV MAKE SURE YOU STATE ALL CONDITIONS FOR NITRATION IF BEZNEN VS OHENOL

A

Benzne = conc nitric cinc sulfuric
AND 50° PLEASE

but phenol just dilute nitric

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12
Q

If an acyl chloride reacts with ohenol what happens?

A

It’s not ACYLATION, instead it is a NEUTRILISATION REACTION

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13
Q

Explain term delocalised pi bond electrons

A

INCORRECR

DELOCLAISED electrons are electrons that are spread over MORE THAN TWO ATOMS

And the pi bond bit is that they are FORMED BY AN OVERLAP OF P ORBITALS !

so electrons that are spread across more than 2 atoms where they are formed by an overlap of p orbitals

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14
Q

How to show bromine as an electrophile ?

A

Show the polar charge
- say it accepts an electron pair if electrophile

  • show example from rando reaction
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15
Q

ALSO ANOTHER REASON FIR WHY BEZNENE LESS READILLY RECATS WITH BROMINE COMPARED TO CYCLOHENE (other than the electron density)

A

ALSO BENZNE MUCH MORE STABLE
- This More Energy needed to react with

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16
Q

If saying write equation and not space then

A

PLEASE USE LETTERS, especially if it says balance

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17
Q

Remember if yield by max is something and you’re working back need to DIVIDE BY 0.45!OR WHATEVER LERCENTAGE YIELD IS

A
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18
Q

Name two types of commercially importsnt material whose manufacture involves nitration of benzne

A
  • pharmaceuticals like paracetamol?
  • dyes / explosives?

So answer is

  • fibres/ dyes/ explosives / Pharma
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19
Q

For nitration what are specific conditions

A

Coco acids so cinc nitric and conc sulfuric

50

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20
Q

What does curly arrows movement mean

A

1) movement of a PAIR OF ELECTROND
2) also breaking or forming a covalent bond

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21
Q

Remember key word for definition of electrophile

A

Accepts a PAIR of electrons

22
Q

Compare number of electrons and nature in benzne vs horseshoe

A

When talking about electrons being DELOCLAISED, always mentioN PI BONDING electrons

1) pi bonding electrons are DELOCLAISED in both structured, yet there are 6 complete wlectrons here in first,
- which spread across the ALL CARBON AROMS

x in second there are only 4 delocalised pi electrons , which spread across 5 CARBONS ( giving it listigerem )

so 1) DELOCLAISED 2) how many) 3 where they spread!

23
Q

How else find rate constant if order 1

A

You know it’s just any rate / any cknc

So if you found grsdient for first conc then just do one over other

Or find ln 2

24
Q

For moles, do the correct calc, then multiply by Avogadro to get total formula mass and then compare

A
25
Q

Don’t assume the charge on NO2 as +!

A

Gotta see how many it connect with other ion, here it wa mg so NO2 is -1 and thus N is 3

26
Q

Remember to check units for the activation energy stuff

A

So like make sure joule vs kilojoules

27
Q

How to say order 0 for straight line on comic time growth

A

Lit jus say it is constant grsifent so zero ordere

Say straight line through 00 correct, also directly proprtionsl and as one increases it increase by same factor

28
Q

BRUV REMEMBER BALACING YOU ARE ALLOWED HALF NUMBERS

A

bun that remember thst it should be balanced I’m the first place 😭😭😭 then it will work out

29
Q

Remember how to find out iverla order if they give units?

A

Just use units and manipulate snd youll findit

30
Q

Catalyst added to system in dynamic equilibrium

A

The rates of friars and backward inc by same amount

Nothing happens to the concentrations!

31
Q

Two ways a catlayst helps chemical companies make processes more sustainable and less harmful

A

Can be carried out at lower temperature which means lower energy demand

And thus less fossil fuels burnt and less co2 emissions

And can reduce use of TOXIC SUBSTANCES

32
Q

Also if it is in the presence of something BUT NOT IN THE EQUATION, can it still pop up in the rate equation?

A

Yh ti can , make sure to use all evidence they give!

33
Q

Also why does a large excess of a reactant mean in terms of orders
OR

A

Most likely that the reactant has no order so haveing large excess means it can be 0 order

Large excess which basically means it’s CONSTANT

OR TO MAKE SURE EQUILIBRIUM POSITION TO THE RIGHT

34
Q

Whenever get graph and maybe dont knowwhat order is, work out half life if it is a curve

A

Half life will mean itd 1st

Not means 2nd

Straight means 0

35
Q

Okay make sure thet if asking in minutes DOMT do conversion

And if they ask for initsl rste snd yiu have rste equation instead of doing tangent business try do

A

Try do rste formula and substitute in

36
Q

Damn how to find kc constant if you don’t have VOLUME so can’t find concentrations but still have moles

A

Well all the volumes say CANCEL out in final division so just do kc but using the moles thstsit

This is because in equilibrium the volume of everything is the same, just different moles?

37
Q

Chlorine risk and benefit for wwter treatment

A

BENEDIT = KILLS BACTERUA AND STERILISED WATER

Risk it can run into plants where CAN FORM chlorinate hydrocarbons can be made which are toxic and carcinogens WHEN RUN OFF

38
Q

Bruv if iodide has higher boiling point and weaker permanent dipole, then the reason for this is because of london firces cmon man

A

PATRERN how read a few time s

39
Q

When showing Boltzmann change usijg temperature, what to make sure to do

A

Right and upwards, mark ea and say popetion ofmmoelcuels with required eamhsd nie increases so rate respirier increases

40
Q

How to do recrystallisation to obtain pure product

A

Dissolve it in min volume of hot water
Cool solution and fikter solid

And wash with cold solvent and let it dry

Check its purity by finding melting point

And comparing it against known values
The closed ti is the more pure it is

41
Q

Trend with mit much actual substance how to shown

A

Just say this the most this the least reactive or jitrwted

42
Q

How to say REASON FOR LESS ELECTRON DENSKTY IN DEACTIVATING GROUPS

A

Say as CooH group is an ELECTRON WITHDRAWING Group , the electron density is lower then BEZNENE so it attracts electrophiles and polarised them less

Phenol partially delocalised increase

43
Q

Remember Mass of the molecules is what on the mass spectrum

A

The Peak at the Right the molecular ion so find molecular formula find the percentage empirical snd kultipyl to ger molecular

44
Q

Why major product formed

A

Because the carbocations formed forms on the carbon with the most alkyl group as thisnis stable most, thus it happens lket his,

45
Q

Get this right man what is the weaker base and what can it only react with

A

The weaker base is the sodium cabrinate so only reacstw ith carbox

Stringer is Na hydrodide and this reacts with BITHN

46
Q

REMEMBER TO WORK OUT EZ BY DRAWING AND CANCELLING EACH OUT

A
47
Q

Oh damn don’t get caught lacking with Ethernet and bromine bonds broken it’s BOTH PINAND SIG,A

A

!! Because pi bond in Alkenes. And sit,a bond in bromine

Remmeber Potsdoum hydroxide can react with ohenol as neutriksaiton !

48
Q

SIMILARITY SND DIFFERENC EWITH KEKULE AND DELOCALISED MODEL for overlap

A
  • bith hsve side on overlap of p orbitals to make pi bonds

But BEZNENE has a system kf pi bonds above snd below

Where as kekelule localised

And alternation linbodjs comsore do delocalised drink shdgem around sll 6

So 2) alternating bs sround all
2) bith ive,ap to make pi bonds

One is local one is delocla

49
Q

Describe 3 evidence

A

2) bond lemthnall the same
2) hydrogenation less than expected for model
3) benzne is less reactive than Alkenes as brominatioj wouldn’t happen without catalyst

50
Q

Okay so we got curly arrow moving up to positbe whatnhspoens

A

Now positbe negative and what was lost 2 so positbe !

51
Q

Hereltotyic fission

A

Both electrons go to one

WHEN A COVSLENT BOND BRESKS

52
Q

Damn add three pronaonesand balance equation ti get same cabrin as before

A

Scatalsyr is it is produced snd msde so not used up too!

a level chemistry year 13 (25 decks)

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