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# Aqa chem 4/ chem 5 june 2016 thread

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1. Whats the equation for cobalt/ copper with excess oh-?
2. (Original post by Jmedi)
They will tell you if it's in alkaline solution
Thanks!
3. Help in my notes, the equation for [Cr(h20)6]3+ with EXCESS OH is [Cr(h20)3(oh)3] + 3OH- --> [Cr(oh)6]3- + 3h2o but this is the mark scheme help??! It's the same with excess nh3 too!!
4. (Original post by Anam)
[Al(h20)6]2+ + OH- ===> [Al(OH)4]- + 3h20

is this equation right for excess oh- being added to aluminium
Al(H2O)3(OH)3 + OH- ===> [Al(OH)4] - + 3H2O
or
[Al(H2O)6]3++ 4OH- ===> [Al(OH)4] - + 6H2O
5. (Original post by Chembio123)
Help in my notes, the equation for [Cr(h20)6]3+ with EXCESS OH is [Cr(h20)3(oh)3] + 3OH- --> [Cr(oh)6]3- + 3h2o but this is the mark scheme help??! It's the same with excess nh3 too!!
Can i see the question and I can see what's up
6. Hi,
For the rechargeable & and non rechargeable cells do we need to learn the species involved in each or we would be given, if a question is asked on it ?
7. (Original post by Super199)
Whats the equation for cobalt/ copper with excess oh-?
i know u get cu(oh)2 and co(oh)2 which are both blue precipitates.

only cobalt can be further oxidised at this point by air or h2o2 to give cr(h20)3(oh)3 which is brown ppte
8. (Original post by Chembio123)
Help in my notes, the equation for [Cr(h20)6]3+ with EXCESS OH is [Cr(h20)3(oh)3] + 3OH- --> [Cr(oh)6]3- + 3h2o but this is the mark scheme help??! It's the same with excess nh3 too!!
Your equation is further substitution after the dilute OH- has been added
Hi,
For the rechargeable & and non rechargeable cells do we need to learn the species involved in each or we would be given, if a question is asked on it ?
The only cell half equations you need to know are the hydrogen fuel cell ones. All the others will be given if asked
10. Guys - if you would recommend I do any 3 CHEM5 papers, which ones would they be? Very short for time - hectic exam timetable
11. (Original post by SirRaza97)
Al(H2O)3(OH)3 + OH- ===> [Al(OH)4] - + 3H2O
12. What are the hydrogen fuel cell equations?
13. (Original post by Boundless_x)
[Al(H2O)6]3++ 4OH- ===> [Al(OH)4] - + 6H2O

it's aliminium 3+ not 2+
14. (Original post by study2016)
Guys - if you would recommend I do any 3 CHEM5 papers, which ones would they be? Very short for time - hectic exam timetable
Any other than June 2015 i would say
15. What colour is
[Cr(NH3)6]3+

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16. why topics from AS are you guys looking back at?
17. (Original post by Kikstar)
Thank you so much! I can now sleep in peace haha. Best of luck in your exams

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No worries! Good luck to you too
18. (Original post by Bloom77)
What colour is
[Cr(NH3)6]3+

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Purple
19. Cobalt with excess OH-: [Co(H2O)6)2+ + 2OH- --> Co(H2O)4(OH)2 + 2H20
20. how do you suss out which species to use as the salt bridge of a cell

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