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

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Original post by C0balt
You should get the mark

That's right
12.5 ans 37. 5 is half neutralisation point where pH=pKa
25 and 50 is right or 12 and 37.5?
Original post by Tomasio
25 and 50 is right or 12 and 37.5?

25 and 50 are the equivalence points/vertical sections
Original post by C0balt
25 and 50 are the equivalence points/vertical sections
yeah, agreed that the vertical sections are at 25 and 50. pka is not 12.5, 37.5?
Reply 1243
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drj24
8
It was harder overall I thought...
Original post by Tomasio
yeah, agreed that the vertical sections are at 25 and 50. pka is not 12.5, 37.5?

pKa are same as pH at half neutralisation points ie at 12.5 and 37.5 indeed
Original post by C0balt
pKa are same as pH at half neutralisation points ie at 12.5 and 37.5 indeed
omds cheers
I got a mark
I think it was the third multiple choice or so, but the question was about 2 mechanisms. Were the answers: bond broken bond formed, racemic mixture ?
Original post by shazza.kk
I think it was the third multiple choice or so, but the question was about 2 mechanisms. Were the answers: bond broken bond formed, racemic mixture ?


Bonds broken


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Reply 1248
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Hdb
Original post by C0balt
pKa are same as pH at half neutralisation points ie at 12.5 and 37.5 indeed

Being super harsh, I think I got 76 at worst.. Do you think this will be an A* 🙏🏻
Original post by Tomasio
omds cheers
I got a mark

Yay
Original post by shazza.kk
I think it was the third multiple choice or so, but the question was about 2 mechanisms. Were the answers: bond broken bond formed, racemic mixture ?

Iirc i think so
Original post by Hdb
Being super harsh, I think I got 76 at worst.. Do you think this will be an A* 🙏🏻

Should be
Original post by C0balt
pKa are same as pH at half neutralisation points ie at 12.5 and 37.5 indeed


Oh I said pka=ph at the first equivalence point/neutralisation :/ btw did you have a clear vertical section for the first equivalence point? I found it difficult cos the starting ph (1.5) and ph of the first neutralisation (1.9) were too close


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Original post by sayshay
Oh I said pka=ph at the first equivalence point/neutralisation :/ btw did you have a clear vertical section for the first equivalence point? I found it difficult cos the starting ph (1.5) and ph of the first neutralisation (1.9) were too close


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Well if you think about it
Ka=[H+][A-]/[HA] and at half neutralisation [A-] =[HA] so the fraction cancels and you get Ka=[H+] so pKa=pH at half neutralisation.
I did, I don't think it was too difficult because it was supposed to be a really gradual rise anyway due to buffer effect
Original post by chemica
Do you unit 4 is harder than unit 5 ? swear down last years unit 5 was piss easy


I got the grade boundaries wrong we're not IAL so its more like 70 for an A i reckon :'( personally unit 4 vs 5 neither is more difficult just depends on the year.
Original post by Hdb
Being super harsh, I think I got 76 at worst.. Do you think this will be an A* 🙏🏻


Wish I was in a position where 76 was my worst case scenario lol...
lads , that multiple chooice question when it was like only one of the mechanisms does this . Was it forms a racemic mixture or was it the one about only one of them leads to elimination . For the tms one i put there are many (12 ) hydrogens , i didnt say they were in the same environment. Would i lose the mark?
Original post by Hdb
Being super harsh, I think I got 76 at worst.. Do you think this will be an A* 🙏🏻


Think it was 78 last year so seeing as response has been less positive you're probably gonna be very close, just need to do well in Unit 5 too
What was the pH question about H2S I can't remember it for the life of me?
(edited 7 years ago)
Reply 1257
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Hdb
Original post by Science&Despair
Think it was 78 last year so seeing as response has been less positive you're probably gonna be very close, just need to do well in Unit 5 too


Thanks bro, really need to do well in unit 5 since I've only scraped an A* in practical too :/
I made so many stupid mistakes :redface:
you know for that question about what is bad in the equilibrium with barium chloride, could you have said the ammonia because it is toxic

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