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OCR A2 CHEMISTRY F324 and F325- 14th and 22nd June 2016- OFFICIAL THREAD

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Fingers crossed OCR gives us 2 easy papers as they're probably focusing on their new spec.
Reply 161
Avatar for AqsaMx
AqsaMx
5
There was a question on electrode potentials in a paper. I can't remember it exactly but it said in alkaline conditions OH- reacted with H+ shifting equilibrium to the other side because the removal of H+ ions made the electrode potential more negative?
Does anyone know why this is or is it just something we should know?
Original post by AqsaMx
There was a question on electrode potentials in a paper. I can't remember it exactly but it said in alkaline conditions OH- reacted with H+ shifting equilibrium to the other side because the removal of H+ ions made the electrode potential more negative?
Does anyone know why this is or is it just something we should know?


I think its if H+ was in the product side of equilibrium and the concentration of it is decreased, the equilibirium will shift to the left to conpensate and reduce EP doing so.
If H+ was on right and it decreased in concentration, the EP will increase
Original post by zirak46
Oh great. Pls f325 dont be hard.


Hahaha hopefully they'll be nice this year seeing as its the last exams of this spec I think...
Original post by Heisenberg___
Hahaha hopefully they'll be nice this year seeing as its the last exams of this spec I think...


I would have thought that's all the reason not to be nice this year. Ah well, we'll find out soon I guess...
Original post by Heisenberg___
How is everyone feeling about the two exams?? After last years papers, I reckon f324 will be slightly easier and f325 marginally harder


I'm worried a massive NMR question on F324 and a horrendous redox titration question on F325 will trip me up :cry2:
Original post by Kamara7
I'm worried a massive NMR question on F324 and a horrendous redox titration question on F325 will trip me up :cry2:


They are literally the worst type of question in each paper!!!

For NMR questions, I just always state the chemical environments, number of protons/carbon atoms in that environment and number of adjacent protons - that always seems to pick up loads of the marks! But I'm really worried that I'll just panic under the pressure :frown:
I've attached part of F325 June 2013 Question 8. Please can someone explain to me the last part? I've correctly solved some of it, but I don't understand the rest. Thanks!
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Reply 168
Avatar for ranz
ranz
5
someone pls tell me what t.m colours we need to know, i learn the ones given but then i find out there r more, its endless!


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Purple green pink green brown purple green blue

All respective to

Ti, Cr, Mn, Fe 2+, Fe3+, Co, Ni, Cu

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Hey can someone please explain two things from this question:

1) how to know which acid with pka would have ph 3.55

2) what does it mean by relative concentrations? How would the final answer be written?

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Original post by Heisenberg___
They are literally the worst type of question in each paper!!!

For NMR questions, I just always state the chemical environments, number of protons/carbon atoms in that environment and number of adjacent protons - that always seems to pick up loads of the marks! But I'm really worried that I'll just panic under the pressure :frown:


This is exactly what I do! It's just annoying that I can't get the last 1 or 2 marks for the structure as I usually don't have enough time :frown: I don't like the titration ones as well because they give you a page to read then there's a question saying "find the mass of X" or something for 6 or more marks :eek: They give you tons of blank space and I just look at it like:

Spoiler

You're not the only one :/


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Reply 173
Avatar for ranz
ranz
5
guys difference between polypeptides and polyamides? besides the linkage what else i different really, its just the same thing reacting together so how come one produces a polypeptide and another an amide linkage?


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Original post by ranz
guys difference between polypeptides and polyamides? besides the linkage what else i different really, its just the same thing reacting together so how come one produces a polypeptide and another an amide linkage?


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Polypeptides are just a type of polyamide - but polypeptides are specifically made of amino acids.
Original post by ranz
guys difference between polypeptides and polyamides? besides the linkage what else i different really, its just the same thing reacting together so how come one produces a polypeptide and another an amide linkage?


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Aren't they the same thing? I thought a peptide bond is an amide bond. Polyamide is an umbrella term which polypeptide comes under, I think polypeptide specifically refers to a polymer of amino acids :smile:
Original post by med456
Does anyone have the f325 2015 past paper & mark scheme? I really need it for revision!


Did you find them?
Pls send pm 😅


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Please anyone send me 2015 papers f321 f322 f324 f325
I'm external so can't ask teacher and I've finished all of the others 😭😭
Pls help me and God will bless you and give you good results


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Original post by Kamara7
Aren't they the same thing? I thought a peptide bond is an amide bond. Polyamide is an umbrella term which polypeptide comes under, I think polypeptide specifically refers to a polymer of amino acids :smile:


Can't polyamides be made from a carboxylic acid and an amine? Whereas polypeptides are made from lots of amino acids specifically, not lots of carboxylic acids and amines.
In weak acids, eq lies more to left due to PARTIAL dissociation.

If not everything dissociated (partial), then obvs equilibirium will be more to left

Get me?

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