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# ocr a f325 revision thread watch

1. (Original post by eggfriedrice)
Will you actually? XD I would take you up on that offer but I gotta wake up early because I have to go into school with my brother for his morning exam (my mum drives us). I woke up at 1 today. -_-"
Oh well, you need your sleep then. Make up for it in college. I'll be sleeping till nine. I remember when I had to do that in college, aaaah good times - it's got to be done.
2. (Original post by kevloui)
2FeO4 2- + 12H+ -----> 2Fe3+ + 6H20 + O2 ??
No but you are getting very close,
3. (Original post by AyshaK)
moles = vol of gas/24 dm3
Yes that's one equation. There are three for moles though aren't they. Depending on what you're given, mass/molar mass or volume or concentration or combination of a few.
4. (Original post by _HabibaH_)
(conjugate base/weak acid) x100 for percentage dissociation
What question would that come under? Buffer?
5. Good luck to you all, I have stupid general studies in the morning, so have to get up early
6. (Original post by otrivine)

I am giving you a very hard demanding question,

Aqueous ferrate (VI) ions Fe04 2- decompose in the presence of hydrogen ions, forming Iron(III) ions, oxygen and water. Construct an ionic equation for this reaction
Fe6+ + 4O2- + 4H+ -> Fe3+ + O2 + 2H2O + e-
7. (Original post by otrivine)
Cause in the book it stated that if a reaction is less than 0.4v a reaction cannot take place, and this is false info
Oh I got told when the standard electrode potential is negative then a reaction isn't feasible
8. cell potentials;
the more positive voltage is the oxidising agent and so is reduced (?)
therefore does that reaction go forwards and the less positive one go backwards?
9. (Original post by _HabibaH_)
Could you explain that a bit more please? I'd like to know what you're saying too!
On June 2010 paper Q6e)
Says C is a gas, at RTP C has mass of 1.17g

I want to know why they did 1.17 x 24
I thought the formula was n= v/24...
10. (Original post by otrivine)

I am giving you a very hard demanding question,

Aqueous ferrate (VI) ions Fe04 2- decompose in the presence of hydrogen ions, forming Iron(III) ions, oxygen and water. Construct an ionic equation for this reaction
4(Fe04)2- + 20H+ ----> 4Fe3+ + 3O2 + 10H20
11. (Original post by _HabibaH_)
Yes that's one equation. There are three for moles though aren't they. Depending on what you're given, mass/molar mass or volume or concentration or combination of a few.
moles = mass / mr
moles = conc x vol
12. (Original post by eggfriedrice)
What question would that come under? Buffer?
That came under Ka and acids in one of the papers.
I cant figure this out.
Basically, dont we have to divide the moles of thiosulfate by 2 to get moles of Cu
The book got the moles of 2Cu^2+

Its page 223 of the OCR book. I attached the image too.
Attached Images

14. (Original post by JimmyA*)
Good luck to you all, I have stupid general studies in the morning, so have to get up early
Same
15. (Original post by Namod)
Fe6+ + 4O2- + 4H+ -> Fe3+ + O2 + 2H2O + e-
No, where did Fe 6+ come from?
16. (Original post by AyshaK)
Oh I got told when the standard electrode potential is negative then a reaction isn't feasible
Like what do you mean sorry?
17. (Original post by otrivine)
No, where did Fe 6+ come from?
Lol
then it must be:

Fe04 2- + 4H+ -> Fe3+ + O2 + 2H2O
18. (Original post by alltimeemilyxo)
cell potentials;
the more positive voltage is the oxidising agent and so is reduced (?)
therefore does that reaction go forwards and the less positive one go backwards?
imagine it as a number line, the more negative, the more to the left so the reaction goes backwards
the more positive, the more to the right so the reaction goes forwards

oxidising agents oxidise other things so are reduced themselves
19. (Original post by otrivine)
No but very close
I changed my answer

2FeO4 2- + 10H+ -> 2Fe 3+ + 3/2 O2 + 5H2O
20. (Original post by eggfriedrice)
I changed my answer

2FeO4 2- + 10H+ -> 2Fe 3+ + 3/2 O2 + 5H2O
yeeeeeeessssssss correct!!!!!!!!!

show us how u did it please

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