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

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Just what wondering what y'all put for the solution you would add for the S2O32-/I2 titration. I put starch but idk seems weird to me
Original post by k.russell
The point still stands even if the numbers aren't exact, I don't believe that 8.3% of my year group in chemistry got over 90% on that exam lol. Also my college consistently performs above average at chemistry. If you ask me, that paper was probably easier than any previous EEE paper APART from 2015, therefore I am expecting boundaries between 2014 and 2015 so somewhere around 92 or 93 for full ums. To say it will be higher than 95 for full ums is a complete and utter joke, especially when you consider that the crazy high ums from last year in EEE was probably caused, at least in part, by the crazy low ums in last years RPA, with 50/60 getting you 90/90UMS

But again, an A* in chemistry averages all 3 units. Most students get near full marks on coursework due to cheating, students will score high on F324 and they don't have to get an A* in F325 to average an A* in Chemistry... Bottom line, 8.3% getting an A* in chemistry is not the same thing as 8.3% getting an A* in F325. And I do believe around 8% of population would get above 88 in that exam (which is my prediction for an A*). A few good private schools will skew the results too.
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Original post by Hughseff
Just what wondering what y'all put for the solution you would add for the S2O32-/I2 titration. I put starch but idk seems weird to me


yeah starch then dark blue to colourless
Original post by BioStudentx
But again, an A* in chemistry averages all 3 units. Most students get near full marks on coursework due to cheating, students will score high on F324 and they don't have to get an A* in F325 to average an A* in Chemistry... Bottom line, 8.3% getting an A* in chemistry is not the same thing as 8.3% getting an A* in F325. And I do believe around 8% of population would get above 88 in that exam (which is my prediction for an A*). A few good private schools will skew the results too.


Stickerline-elsa-let-it-go.png
Do you get marks for an answer that is correct but crossed out and an alternative answer is given?
Original post by Haiku786
Do you get marks for an answer that is correct but crossed out and an alternative answer is given?

If you crossed out a correct answer and wrote an alternative that is incorrect - no, you won't get marks for the crossed out correct answer.
Original post by steph-carys
Well I actually got around -1176 and most people are saying -1099 which I'm guessing is correct as the majority have it. And I can't see what I would've done to f up..


I got that answer too and I definitely doubled the value for hydration of K so not sure what went wrong
Original post by smartalan73
I got that answer too and I definitely doubled the value for hydration of K so not sure what went wrong


Wait, you got -1176?1 :redface: cause my other friend got this too! And I'm racking my brain on where I could've gone wrong... maybe something to do with signs?
what did everyone put for the last Q when they asked for a suitable copper compound and its ionic and overall equation?
Original post by steph-carys
Wait, you got -1176?1 :redface: cause my other friend got this too! And I'm racking my brain on where I could've gone wrong... maybe something to do with signs?

The most logical reason I can think of is that you messed up with the delta H solution? It was a low number 30 or 20 something so you could have rearranged it wrong?
Original post by smartalan73
I got that answer too and I definitely doubled the value for hydration of K so not sure what went wrong

I think that might be because you did lattice enthalpy= enthalpy of sol +enthalpy of hyd + enthalpy of hyd. And then rearranged. It should be LE +SOL= HYD+HYD. And then rearrange.
Original post by LaraDresser
I know you had to use Cr3+ in your answers... it was about using Cr3+ as a reducing or oxidising agent. Are we talking about the same question?


Yes we are... you only provide thw two possible equations which is what I said. Cr3+ cant be oxidised in system two you do know that right?Cr2+ can get oxidised in system two which is why we look at equation 6 where it had cr3+ being oxidised to 6+ but the feO4- one,7

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Original post by steph-carys
Wait, you got -1176?1 :redface: cause my other friend got this too! And I'm racking my brain on where I could've gone wrong... maybe something to do with signs?


I can tell you what I did with letters. Ignoring negatives and using all positive numbers I did A+B-2C=D. I think A, C and D were all negative and B was positive but I just used all positive values and tried to use the diagram since the lines A and B combined seemed to make the lines C and D combined
Yh! You're right I don't think 6 or 7 had cr3+ in it! 🤔🤔🤔
Original post by LaraDresser
I know you had to use Cr3+ in your answers... it was about using Cr3+ as a reducing or oxidising agent. Are we talking about the same question?
Original post by Haiku786
I think that might be because you did lattice enthalpy= enthalpy of sol +enthalpy of hyd + enthalpy of hyd. And then rearranged. It should be LE +SOL= HYD+HYD. And then rearrange.


Yes that would be it!! I always hated the solution born haber cycles, can do the formation ones but always had a problem with these! I believe I did LE = SOL +HYD
Original post by smartalan73
I can tell you what I did with letters. Ignoring negatives and using all positive numbers I did A+B-2C=D. I think A, C and D were all negative and B was positive but I just used all positive values and tried to use the diagram since the lines A and B combined seemed to make the lines C and D combined


Can't quite remember what I did, I think maybe I did HYD + HYD +SOL= LE so it was probably just a sign problem? :tongue: hopefully I will still get some marks
(edited 7 years ago)
Original post by steph-carys
Yes that would be it!! I always hated the solution born haber cycles, can do the formation ones but always had a problem with these! I believe I did LE = SOL +HYD


and was one of them 2x hydration??
In your diagram did you also put 2x one of the letters?
Original post by smileez_101
and was one of them 2x hydration??
In your diagram did you also put 2x one of the letters?


Yes, I definitely doubled the hydration for potassium :tongue:
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Original post by smileez_101
what did everyone put for the last Q when they asked for a suitable copper compound and its ionic and overall equation?


like copper sulphate and it forms sulphuric acid and cu(hcoo)2
Original post by nimoooooooo
Yh! You're right I don't think 6 or 7 had cr3+ in it! 🤔🤔🤔


Yes equation 6 did. Cr2O7 2- <---> Cr3+
obviously including the h20s and stuff

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