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AQA - Unit 5 - Energetics, Redox and Inorganic Chemistry

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Reply 560
Avatar for jamest92
jamest92
Original post by Wish I Could Change This
How on earth is everyone remembering the colour changes for complex ions?


Personally i just wrote all the colours and equations out over and over again. Takes the piss but they've managed to stick so far
Reply 561
Avatar for SSM
SSM
I am also struggling with long calculations

Question 8c

http://store.aqa.org.uk/qual/gce/pdf/AQA-CHEM5-W-QP-JAN10.PDF

Thanks :biggrin:
This was in the in tha jan 2011 paper it says,
This is the reation at the positive electrode:
Li+ + CoO2 + e- > Li+... etc

But I was told that the positive ion, is attracted to the negative elctrode?

damm im confused

anyone???
Reply 563
Avatar for Tigerkins
Tigerkins
Original post by Somali-Pir8
does anyone know the colour of [FeCl4]-
can't find this particular one in any of my notes or textbooks


I think it's yellow.
Original post by Arab_Empress
Why does red light get reflected if blue light is absorbed?


It's just frequencies of light,
I think it goes from red to blue to UV etc
They're just opposite ends of the visible light frequencies :smile:
Reply 565
Avatar for Sheldon
Sheldon
7
Original post by Arab_Empress
Why does red light get reflected if blue light is absorbed?

It doesn't all the time, it depends on what compound it is, as each TM metal has a different number of outer 3d electrons so can excite to different levels so will give out light of a range of frequencies

AHH alevel physics helps here
Reply 566
Avatar for NRican
NRican
Original post by Sheldon
:smile:


Thanks a lot both of you, Much appreciated :smile:

Any chance you can help me with
Question 8c

http://store.aqa.org.uk/qual/gce/pdf/AQA-CHEM5-W-QP-JAN10.PDF
especially the 1/4 bit

I am rubbish at calculations :frown:
Original post by jamest92
Personally i just wrote all the colours and equations out over and over again. Takes the piss but they've managed to stick so far



You reckon it's do-able in a day? :colondollar:
Original post by Somali-Pir8
does anyone know the colour of [FeCl4]-
can't find this particular one in any of my notes or textbooks


No need to know it.
Original post by Sparkly-Star
Me too :love: I started with 15 for the same reason, I find 16 easier. Luckily I had to do tons of revision on chapter 15/16 for my ISA so I don't find them too bad.
Yeah I don't think the difficulty will change a lot, the grade boundaries seem to stay around the same numbers. :yep:
Hmm on another note, where are all the chem people? The bio thread was full!


Hopefully the grade boundaries they stay like that or go even lower lol :biggrin:
I think they are finally filtering into the thread, but it did take a long time for me to find this cause its not under CHEM5

Original post by Sparkly-Star
Has everyone memorized 15.4/15.5? :colondollar:


I haven't learnt them, It's easier to learn how to balance half equations.

Like for potassium manganate I learn MnO4- --> M2+ and then just balance it with H2O, H+ and e-, Its the same with dichromate ...

Btw sorry for the late reply I have being trying to finish Chapter 16, which I've done now. And a random question, on 5e i) of JUN 10, how do you know the initial and final colours. Is it because all aqueous Cu2+ ions form hexa aqua ions? But what about the final colour....don't worry if you don't know :smile:
I hope we get analysis of iron tablets. :p:
understand the importance of variable oxidation states in
catalysis; both heterogeneous and homogeneous catalysts'

anyone give me help with this??
Reply 572
Avatar for jamest92
jamest92
Original post by Wish I Could Change This
You reckon it's do-able in a day? :colondollar:


Dont see why not, what i did was pick a metal then write down all the different formuale and colours you need so hex aqua, OH- and NH3, OH- in excess, NH3 in excess, carbonate ions and Cl- for cobalt and copper, and just repeat them all over the page, turn over and do the next metal. Once you've done all 6 take a break and come back and try and do them from memory, just keep at it and it should click eventually.
Reply 573
Avatar for jamest92
jamest92
Original post by Gertius Maximus
understand the importance of variable oxidation states in
catalysis; both heterogeneous and homogeneous catalysts'

anyone give me help with this??


I think all that means is be aware that the reason catalysts work is because of variable oxidation states meaning they can transport electrons
Reply 574
Avatar for Sheldon
Sheldon
7
Original post by NRican
Thanks a lot both of you, Much appreciated :smile:

Any chance you can help me with
Question 8c

http://store.aqa.org.uk/qual/gce/pdf/AQA-CHEM5-W-QP-JAN10.PDF
especially the 1/4 bit

I am rubbish at calculations :frown:


I have not checked the mark-scheme so i don't know if this is right but here is my attempt
photo.jpg510.1KB
Original post by jamest92
Dont see why not, what i did was pick a metal then write down all the different formuale and colours you need so hex aqua, OH- and NH3, OH- in excess, NH3 in excess, carbonate ions and Cl- for cobalt and copper, and just repeat them all over the page, turn over and do the next metal. Once you've done all 6 take a break and come back and try and do them from memory, just keep at it and it should click eventually.


completely forgot we had to learn the Cl- as well, thanks. I WILL get this done, I have a fun day ahead of me... :biggrin:
Original post by Sparkly-Star
No need to know it.

why not
we need to know all of the other reactions/colours


Original post by Tigerkins
I think it's yellow.

cheers, just trying to memorise it all last minute:biggrin:
Original post by Sheldon
Electron will absorb Photons of light, the gain energy equal to the energy the photon had according to E=hf
when the electrons have this energy they enter an exited state where they move up the energy levels in the orbitals, after a given time they will de-excite fall down the levels and release photons of light, these will have a different frequency to the ones taken in as some energy was used going up the energy levels and as E-hf the frequency has to change. So in Transition metals they give out light in the visible part of the spectrum.
It all depends on what frequency of light is given out because each colour has its won frequency.


Thank you very much :smile:
Reply 578
Avatar for jamest92
jamest92
Original post by Wish I Could Change This
completely forgot we had to learn the Cl- as well, thanks. I WILL get this done, I have a fun day ahead of me... :biggrin:


Good luck, i expect you to be able to rattle them all off from memory by tonight
Original post by GoodOl'CharlieB
Hopefully the grade boundaries they stay like that or go even lower lol :biggrin:
I think they are finally filtering into the thread, but it did take a long time for me to find this cause its not under CHEM5



I haven't learnt them, It's easier to learn how to balance half equations.

Like for potassium manganate I learn MnO4- --> M2+ and then just balance it with H2O, H+ and e-, Its the same with dichromate ...

Btw sorry for the late reply I have being trying to finish Chapter 16, which I've done now. And a random question, on 5e i) of JUN 10, how do you know the initial and final colours. Is it because all aqueous Cu2+ ions form hexa aqua ions? But what about the final colour....don't worry if you don't know :smile:


I can remember the balancing ones easily but the ones with e.g. H2O2 are a pain to remember. :p: I've finished chapter 15 then I'm gonna do 16. :p: Hmm I'm not sure about the answer to do that! It looks like something from unit 2. I don't know sorry. :colondollar:

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