The Student Room Group
<a https://www.thestudentroom.co.uk/showthread.php?t=7467335'> Year 12s: what will be the first way you research your future options? >>
<a https://www.thestudentroom.co.uk/showthread.php?t=7467335'> Year 12s: what will be the first way you research your future options? >>
<a https://www.thestudentroom.co.uk/showthread.php?t=7467335'> Year 12s: what will be the first way you research your future options? >>

OCR Chemistry A Exam Thread (Breadth - May 27 2016 and Depth - June 10 2016)

Scroll to see replies

Original post by asinghj
Oh ok.. I do maths and physics and I hate physics too. Chemistry is my favourite. Biology I hate, but I think I didn't do too bad on the papers


How did you find OCR Physis. i thought depth was really good
Original post by Jitesh
Depends on what they give you
Cl radical + Cl radical -> Cl2 is one for Cl catalysis

Could be CF2Cl radical + CF2Cl radical -> C2F4CL2 as well for the example earlier


Ok so just wanted to confirm if this random example is right

Initiation :
CF2Cl2 -> CF2Cl• + Cl•

Propagation:
Cl• + O3 -> ClO• + O2
ClO• + O -> Cl• + O2

Termination:
Cl• + Cl• -> Cl2
CF2Cl• + CF2Cl• -> C2F4Cl2

Did I miss anything out? Also should there be a 3rd termination?
Original post by maxross
How did you find OCR Physis. i thought depth was really good


Our college did AQA for physics and that was horrible! That's great that you found Physics good
Original post by asinghj
Ok so just wanted to confirm if this random example is right

Initiation :
CF2Cl2 -> CF2Cl• + Cl•

Propagation:
Cl• + O3 -> ClO• + O2
ClO• + O -> Cl• + O2

Termination:
Cl• + Cl• -> Cl2
CF2Cl• + CF2Cl• -> C2F4Cl2

Did I miss anything out? Also should there be a 3rd termination?


ClO• + ClO• -> Cl2O2
Original post by asinghj
Our college did AQA for physics and that was horrible! That's great that you found Physics good


oh yeah i have heard about AQA. did you have to cross out a question or something?? haha
Original post by 4nonymous
ClO• + ClO• -> Cl2O2


I was thinking that but didn't know you could have Cl2O2
Original post by maxross
oh yeah i have heard about AQA. did you have to cross out a question or something?? haha


Haha yeah. The question was about identifying the properties of a particle (strangeness, Barton number and charge) which was a question I could have done had AQA not messed it up!
What 3 main topics does everyone think will come up? Just want to do some last minute revision on the most probable topics.
Original post by asinghj
Haha yeah. The question was about identifying the properties of a particle (strangeness, Barton number and charge) which was a question I could have done had AQA not messed it up!


how did they mess it up?? what was wrong with it
Original post by bencoughlin
What 3 main topics does everyone think will come up. Just want to do some last minute revision on the most probable topics.


Reaction mechanisms
Spectroscopy
Bonding (intermolecular forces, etc)
But 3 get 1 free:
Physical trends
Original post by asinghj
I was thinking that but didn't know you could have Cl2O2


All you have to remember for termination is that you just put two radicals together.
Although could you also do:
CF2Cl• + Cl• -> CF2Cl2?
Maybe some others?
Although they don't tend to ask you for all the termination steps, usually just one or two so should be fine
Original post by asinghj
Reaction mechanisms
Spectroscopy
Bonding (intermolecular forces, etc)
But 3 get 1 free:
Physical trends

thanks
Original post by maxross
how did they mess it up?? what was wrong with it


pi- + proton -> K0 + X
The interaction was strong so strangeness conserved
We had 4 options 2 were
C: 0, B: 1, S:-1
C: 0, B: 1, S: 1

Now both could be right as K0 could be down andtistrange or strange andtidown so both options were correct
Original post by asinghj
pi- + proton -> K0 + X
The interaction was strong so strangeness conserved
We had 4 options 2 were
C: 0, B: 1, S:-1
C: 0, B: 1, S: 1

Now both could be right as K0 could be down andtistrange or strange andtidown so both options were correct


haha jesus AQA. Hope we don't get that today
Original post by 4nonymous
All you have to remember for termination is that you just put two radicals together.
Although could you also do:
CF2Cl• + Cl• -> CF2Cl2?
Maybe some others?
Although they don't tend to ask you for all the termination steps, usually just one or two so should be fine


Ok thanks that's fine
Original post by maxross
haha jesus AQA. Hope we don't get that today


OCR won't do that
Original post by asinghj
Ok so just wanted to confirm if this random example is right

Initiation :
CF2Cl2 -> CF2Cl• + Cl•

Propagation:
Cl• + O3 -> ClO• + O2
ClO• + O -> Cl• + O2

Termination:
Cl• + Cl• -> Cl2
CF2Cl• + CF2Cl• -> C2F4Cl2

Did I miss anything out? Also should there be a 3rd termination?


Not sure if you would include Cl radical and ClO radical as it is an intermediate but I guess so
Reply 857
Avatar for Cherx
Cherx
20
Original post by Jitesh
Yeah just write it out a couple times

For ozone depletion, Cl and NO radicals are the main ones they ask about

CFCs split by homolytic fission to form a Cl radical (depends what they give etc)... it's the Cl itself that's mainly responsible rather than the other radical formed

E.g. CF3Cl -> CF3 Radical and Cl Radical (under UV)


Yep got it now. Just going over mechanisms now. Is nucleophilic a heterolytic fission?
(edited 7 years ago)
Is shapes of molecules likely to come up?
Original post by Cherx
Yep got it now. Just going over mechanisms now. Is nucleophilic a heterolytic fission?


yes, free radical substitution is homolytic
electophilic addition and nucleophillic substitution are heterolytic

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you