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Edexcel A2 Chemistry Exams -6CH04 (14th June) and 6CH05 (22nd June) Discussion Thread

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Reply 80
Original post by PlayerBB
You need to know all organic reactions, tests, flame test, brief information about redox and Intermolecular forces, electron configuration, I don't know if there's anything else. Same I haven't revised for As yet :frown: it's just so annoying, there is so much to revise for each subject

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Pretty sure you it is unnesasary to be going over flame tests lol.
Reply 81
Original post by usman.zubair
Thats true :tongue: but i think boundaries will be very high. As this is the last exam session for this series & many would be repeating OR giving complete chem A levels. So have to take it srsly :\
so you think chem4 and 5 boundaries will be extremely high this year?
Original post by Tomasio
so you think chem4 and 5 boundaries will be extremely high this year?


No.im talking about unit 1 there.

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Original post by Tomasio
Pretty sure you it is unnesasary to be going over flame tests lol.


Lol, that depends on which exam board are you, for Edexcel you definitely have to revise flame tests
Can someone help me with this, I thought It is Phenol because it is slightly soluble in water but very soluble in HCl but that complex with Cu2+ confuses me
Reply 85
Original post by PlayerBB
Can someone help me with this, I thought It is Phenol because it is slightly soluble in water but very soluble in HCl but that complex with Cu2+ confuses me

The amine because amines form coloured complex with Cu2+ ions. Adding aqueous copper sulphate is a functional group test iirc. And I am guessing phenylamine is more soluble in HCl than it is in water because it is protonated and gains charge, more easily hydrated. But not sure if I'm right.
I remember doing that question though
Original post by C0balt
The amine because amines form coloured complex with Cu2+ ions. Adding aqueous copper sulphate is a functional group test iirc. And I am guessing phenylamine is more soluble in HCl than it is in water because it is protonated and gains charge, more easily hydrated. But not sure if I'm right.
I remember doing that question though


Can you remind me of this functional group test with copper sulphate, I can't seem to remember it!!

And yeah, that seems like a reasonable explanation, thank you!! And lol you have a good memory I guess :tongue:
Reply 87
Original post by PlayerBB
Can you remind me of this functional group test with copper sulphate, I can't seem to remember it!!

And yeah, that seems like a reasonable explanation, thank you!! And lol you have a good memory I guess :tongue:


Well if adding [Cu(H2O)6]2+ to an organic compound gives blue precipitate (green if phenylamine) then it's got an amine group
Can someone add me to chemistry unit 1 thread:smile:
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(edited 7 years ago)
Original post by C0balt
Well if adding [Cu(H2O)6]2+ to an organic compound gives blue precipitate (green if phenylamine) then it's got an amine group


Ahh thank you Cobalt :h:

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Reply 90
Original post by PlayerBB
Lol, that depends on which exam board are you, for Edexcel you definitely have to revise flame tests
huh? I do edexcel and have never seen it u 5 past papers.
Original post by Tomasio
huh? I do edexcel and have never seen it u 5 past papers.


Okay but Edexcel are unpredictable so it's better to know them just in case......

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Reply 92
Original post by PlayerBB
Okay but Edexcel are unpredictable so it's better to know them just in case......



That they definitely are and very good at it too as seen in the Unit 6 paper!


What's the problem here? Like you are unable to solve the sum?


Could you link me to the markscheme for this question please. I'd like to check my answer
Reply 97
Original post by sabahshahed294
What's the problem here? Like you are unable to solve the sum?


I just don't really know what to do and how to use all the data ive been given (and why ive been given those data).
Original post by ST_123
I just don't really know what to do and how to use all the data ive been given (and why ive been given those data).


First of all, you have the volume of the titre and the volume of HCl, find the number of moles for the base and the HCl using n=cv. This is done so as to get the moles of ethanoic acid remaining after reacting with NaOH as it's stated that NaOH reacts with both the acids with the word "both" being in bold. Now, once you get the moles, you take the difference of the moles of HCl and NaOH. Now that you have the moles remaining(for ethanoic acid), this is the no of moles at equilibrium for ethanoic acid. Then check the difference of the initial moles and the moles at equilibrium as well. This is to get the moles that have reacted and hence you'll get the moles of the alcohol and ester. For water, you already have the moles and now just you got to add up simply. Substitute the moles in your Kc expression as volume cancels out!
(edited 7 years ago)
Reply 99
Original post by sabahshahed294
First of all, you have the volume of the titre and the volume of HCl, find the number of moles for the base and the HCl using n=cv. This is done so as to get the moles of ethanoic acid remaining after reacting with NaOH as it's stated that NaOH reacts with both the acids with the word "both" being in bold. Now, once you get the moles, you take the difference of the moles of HCl and NaOH. Now that you have the moles remaining(for ethanoic acid), this is the no of moles at equilibrium for ethanoic acid. Then check the difference of the initial moles and the moles at equilibrium as well. This is to get the moles that have reacted and hence you'll get the moles of the alcohol and ester. For water, you already have the moles and now just you got to add up simply. Substitute the moles in your Kc expression as volume cancels out!


Thanks i did the question now. Although i still don't quite understand how finding the mol of hcl and naoh and subtracting the two gives me the mol left in equilibrium of ethanoic acid.

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