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

1. 1 and 2,6 and 7 were the two equations needed

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2. (Original post by HFancy1997)
1 and 2,5 and 6 were the two equations needed

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We're 5 and6 the dichromate one and the Fe one?
3. (Original post by yiz)
We're 5 and6 the dichromate one and the Fe one?
Sorry I meant 6 and 7, edited now

But it was CrO7 <----> Cr3+
and the FeO4- one for 6 and 7

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4. (Original post by HFancy1997)
Sorry I meant 6 and 7, edited now

But it was CrO7 <----> Cr3+
and the FeO4- one for 6 and 7

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Thanks so much
5. Has an unofficial mark scheme been made yet?
6. Is there an unofficial markscheme ?

A*- 85
A- 77
B- 69
C- 61
D- 53
E- 44
8. (Original post by GetOverHere)
Calculate moles of acid and conjugate base, divide by 1000 to get concentration, use Kaacidoversalt to get [H+], - log to get 3.43 IIRC

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why do you have to work out concentration, didnt they give you the concentrations of the acid
9. (Original post by lukemurp890)

A*- 85
A- 77
B- 69
C- 61
D- 53
E- 44
Yeah I thought these too lol.

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10. For the redox 6 marker, i thought that we had to write the equation with each system and i wrote 2 with each system. Would i still get yhe mark for the 2 equations that we were actually meant to write or will it be marked wrong?
11. (Original post by rachelsmith12)
why do you have to work out concentration, didnt they give you the concentrations of the acid
original concentration not concentration in buffer
12. For the electrode potential question. I just defined reducing and oxidising agents then gave one example of Cr reducing and oxidising from the table. Is that right ?
13. (Original post by Alexander24)
For the electrode potential question. I just defined reducing and oxidising agents then gave one example of Cr reducing and oxidising from the table. Is that right ?
Yes, but there was only one feasible reaction for each of reduction and oxidation. If you chose from multiple 'examples' then you probably went wrong somewhere.
14. Err why are people saying its 1&2 and 5&6 for the redox question? Can someone explain pls? Cuz I thought they asked you to look at half equations 1-6 and see which ones cr3+ will be acting as an oxidising agent or a reducing agent?
15. (Original post by Mo_tunrayo)
Err why are people saying its 1&2 and 5&6 for the redox question? Can someone explain pls? Cuz I thought they asked you to look at half equations 1-6 and see which ones cr3+ will be acting as an oxidising agent or a reducing agent?
That's exactly what you have to do. And the only ones which can be used are 1/2 and 6/7. The others were not feasible.
16. (Original post by marioman)
That's exactly what you have to do. And the only ones which can be used are 1/2 and 5/6. The others were not feasible.
Dont you mean 6 and 7??? Cr2O7 one and FeO4' one??

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17. (Original post by HFancy1997)
Dont you mean 6 and 7??? Cr2O7 one and FeO4' one??

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Yeah, those were the ones. I was just going off his post which said 5 and 6.
18. (Original post by marioman)
Yeah, those were the ones. I was just going off his post which said 5 and 6.
Ahh phew, had me worried for a sec

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19. Grade boundary predictions?? I'm thinking 75/76 for an A
20. (Original post by marioman)
Yes, but there was only one feasible reaction for each of reduction and oxidation. If you chose from multiple 'examples' then you probably went wrong somewhere.
i used correct examples, an electrode potential less than Cr for oxidising agent and greater than Cr for reducing agent

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