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# ocr a f325 revision thread watch

1. (Original post by Kat12395)
WE HAVE FINISHED THE MARK SCHEME (Finally!)
YOU'RE WELCOME!
Thanks alot
2. Anyone know generally what the raw mark will be for 150 ums? Usually I just scale up the difference between boundaries like this (from Jan 13):

60% - C - 56
70% - B - 63
80% - A - 70

Difference between grades is 7 marks, so extrapolating gives...

90% - A* - 77
100% - 84

Reckon this is a valid method to use?
3. (Original post by Raj Kang)
No your wrong because kc can decrease by increasing concentration of reactants and decreasing the concentration of products it's all in the question
Kc is a constant - it's value cannot change.
4. (Original post by Thatasianguy)
does anyone remember the values for the Kc question, i just want to reconstruct it and see what i got.
The values like the equilibrium concentrations and the volume
Volume was 1dm3
I think it was 2x10-3 for H2 at start, then 3x10-4 at equilibrium
Then maybe 4x10-3 I2
5. (Original post by Kat12395)
WE HAVE FINISHED THE MARK SCHEME (Finally!)
YOU'RE WELCOME!
thanks a lot!!!! now I can relaxed
6. (Original post by Kat12395)
WE HAVE FINISHED THE MARK SCHEME (Finally!)
YOU'RE WELCOME!
thank you, a quick question for h2o not added, I put because it is not in the rate equation?

I put Deta G> Tdeta S

you put TdetaS < Deta G means same thing right?
7. (Original post by TauMuon)
Anyone know generally what the raw mark will be for 150 ums? Usually I just scale up the difference between boundaries like this (from Jan 13):

60% - C - 56
70% - B - 63
80% - A - 70

Difference between grades is 7 marks, so extrapolating gives...

90% - A* - 77
100% - 84

Reckon this is a valid method to use?
Yes the difference between grades (deciles) is always the same.
8. (Original post by Kat12395)
WE HAVE FINISHED THE MARK SCHEME (Finally!)
YOU'RE WELCOME!
Fantastic!
Thank you to everyone that contributed!
9. For the optical isomerism i put the right structure but did not put brackets, line in the middle and the charge of the ion how many marka out of three will i get
10. (Original post by Kat12395)
WE HAVE FINISHED THE MARK SCHEME (Finally!)
YOU'RE WELCOME!
Some edits:
The cell potential is 2.71, not 1.71 - the values were -2.34 and 0.37
Redox reactions:
2I- + 2Fe3+ --> I2 + 2Fe2+
2Al + 3I2 --> 6I- + 2Al3+
Al + 3Fe+ --> Al3+ + 3Fe2+

Fe3+ + 3Cl- --> FeCl3(s) - the product must have no overall charge because it is insoluble.

Ionic equation of Al and acid: 2Al + 6H+ --> 2Al3+ + 3H2
11. (Original post by Kat12395)
WE HAVE FINISHED THE MARK SCHEME (Finally!)
YOU'RE WELCOME!
Ooh, I think I remember one of the questions that could contribute to the 5 marks!
Was there a question after calculating delta S about calculating delta G for the reaction at 298 K?
Thank you again for doing the mark scheme though, it's much appreciated!
12. (Original post by Kat12395)
WE HAVE FINISHED THE MARK SCHEME (Finally!)
YOU'RE WELCOME!
Thank you for all your time and help, I feel from this that I've only dropped 14 marks at a push which is great to know, is there still parts that are missing though?
13. FAILED
14. The bidentate ligand: Did it have to be the E-isomer or could it have been the Z? As in would this be acceptable?
15. (Original post by Jack9909)
The bidentate ligand: Did it have to be the E-isomer or could it have been the Z? As in would this be acceptable?
That's not only acceptable, it's correct . If I remember, it showed you the structure?
16. On the unofficial mark scheme, isn't the lattice enthalpy -3800 something?
17. (Original post by PythianLegume)
That's not only acceptable, it's correct . If I remember, it showed you the structure?
Just double checking as the mark scheme they made showed it differently
I wasnt sure if there could be rotation of the C-C bond as its not a double bond
18. Have you (whoever wrote the mark scheme) included the electron configuration? Maybe I missed it in your mark scheme?

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19. (Original post by Jack9909)
Just double checking as the mark scheme they made showed it differently
I wasnt sure if there could be rotation of the C-C bond as its not a double bond
Ignore me Im getting mixed up and confused with questions! Haha
20. (Original post by Amz1217)
On the unofficial mark scheme, isn't the lattice enthalpy -3800 something?
No, They've got the right figure, people are in agreement.

(Original post by Jack9909)
Just double checking as the mark scheme they made showed it differently
I wasnt sure if there could be rotation of the C-C bond as its not a double bond
Are you sure you're not confusing the two ligands - the one with nitrogen in it is shown as a trans isomer in the unofficial mark scheme.

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