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AQA - Unit 5 - Energetics, Redox and Inorganic Chemistry

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Original post by choc1234
how do you know when to write h2o and h+ in cell diagrams?


If its in the original half equation you add it in the cell diagram.
Reply 1061
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Ebony_x
Anyone have any ideas how to do question 3bi in the specimen paper? I thought it was V3+ as the species present, but its clearly not!??
Reply 1062
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NRican
Original post by NRican
Cr with excess NH3 is insoluble right?


?

Book says CrNH306 is a purple soln??
Original post by Ebony_x
Anyone have any ideas how to do question 3bi in the specimen paper? I thought it was V3+ as the species present, but its clearly not!??


See post number 113 (page 6) :smile:
Off to sleep, good luck everyone :smile:
Original post by Ebony_x
Yeah they do alright! Hope we get a good paper tomorrow! :redface:


Good Luck!
Reply 1066
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Ebony_x
Original post by SittingOnCornflakes
Good Luck!


Good luck to you as well! :smile:
I'm getting tired. :frown:
Original post by Luke0011
I'm getting tired. :frown:


Me too, don't give up, it's almost over. :hugs:

(Hello fellow med applicant :jive:)
Original post by Sparkly-Star
Me too, don't give up, it's almost over. :hugs:

(Hello fellow med applicant :jive:)


I'm a REapplicant now haha!

I may be going to sleep soon, i think i've done enough revision! if i dont know it now i wont know it tomorrow! :P
Reply 1070
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Ebony_x
Original post by jimmy303
See post number 113 (page 6) :smile:


Wow you an absolute genius to work that out thanks and repped! :biggrin:
I wouldnt of thought of it like that, I just see V2+ as reducing agent and that gets oxised into v3+, but this clearly just keeps getting oxidsed.. dont quite get how MnO2 can do this though?
Original post by Luke0011
I'm a REapplicant now haha!

I may be going to sleep soon, i think i've done enough revision! if i dont know it now i wont know it tomorrow! :P


Aww yeah, I wish I could've taken a gap year, I'm just going for my back-up. Good luck tomorrow. Yeah haha that's why I am going over it once more before bed and once more before exam tomorrow. Too much to remember. :p:
What do we need to know about non/rehargeable/fuel etc cells? Can someone please summarise the main points?? The spec isn't clear enough :/ Thanks :smile:
quick peeps
(Al(OH)4)^-..or...(Al(OH)6)^3-
Original post by strawberry_cake
What do we need to know about non/rehargeable/fuel etc cells? Can someone please summarise the main points?? The spec isn't clear enough :/ Thanks :smile:


textbook says we dont need to know them in detail so..i don't anyway :tongue: spec just says "appreciate", i think tey'll just give us something to apply knowledge of electrochemical cells to,not ask "what is a daniell cell " or someething. well hopefully anyway :L
Original post by Luke0011
I'm getting tired. :frown:

Me too :frown:

Original post by Sparkly-Star
Aww yeah, I wish I could've taken a gap year, I'm just going for my back-up. Good luck tomorrow. Yeah haha that's why I am going over it once more before bed and once more before exam tomorrow. Too much to remember. :p:


Aw what happened to the all nighter?? :tongue: although I'm getting very tired too, I think its just the boringness of chem5 :/ I still have chaps 13-16 to review over and mod1 :cry2:

EDIT : And that table.. I can never remember the colours :frown:
Reply 1076
Avatar for Mazii
Mazii
Gooooodnight; too much chemistry in my head. It hurts.
Original post by chrissyyip
quick peeps
(Al(OH)4)^-..or...(Al(OH)6)^3-


1st
Original post by Ebony_x
Wow you an absolute genius to work that out thanks and repped! :biggrin:
I wouldnt of thought of it like that, I just see V2+ as reducing agent and that gets oxised into v3+, but this clearly just keeps getting oxidsed.. dont quite get how MnO2 can do this though?


It's like when you add zinc and HCl to Cr2O7(2-)

Cr2O7(2-) is reduced to Cr3+ (orange to green) and is then oxidised again by zinc and HCl to Cr2+ (blue) though this is unstable and oxidises back to Cr3+ if air is present.

In the question it says MnO4- is in excess so although some is used up to oxidise V2+ to V3+ (making Mn2+) there is still some MnO4- left over.

Remember to check the electrode potentials. The MnO4-/Mn2+ electrode is more positive than all the reactions involving vanadium ions so MnO4- will always oxidise any vanadium ions present :smile:
Reply 1079
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NRican
Why are some electron affinity endo and some exo?

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