AQA - Unit 5 - Energetics, Redox and Inorganic Chemistry

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

Me too



Aw what happened to the all nighter?? 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

EDIT : And that table.. I can never remember the colours

Ok, so I have learnt/revised pretty much everything answering exam style questions from the book. I have reached the dreaded Metal Aqua Ions and Colours ...
Is there a way of Learning and remembering this ?? Any good techniques which you have used ? Diagrams etc.. Appreciated.

I'll be here.

Table, the easy way for me anyway let's hope it works for you:

Associate the 6 reactions with numbers 1 - 6, little OH^-, excess OH^-, little NH3, excess NH3, CO3^2-, conc. HCl

Now take one of the 6 metal aqa ions you need to know...

E.g. [Fe(H2O)6]^2+, write down 1 to 6 each time you get a question, first write down the formulas each one produces in each reaction you can easily learn it by just learning the ones that change, then do the colours. The Fe ones should be easy to learn.

Group Cu and Co together cos they're special, they react with Cl- as well.

Al goes on it's own cos really it ain't a transition metal.

Cr, is the other odd one out cos it has loads of formulas.

The M^2+ ones form MCO3.
The M^3+ ones don't and effervescence.

See above.

Ok, so I have learnt/revised pretty much everything answering exam style questions from the book. I have reached the dreaded Metal Aqua Ions and Colours ...
Is there a way of Learning and remembering this ?? Any good techniques which you have used ? Diagrams etc.. Appreciated.

Hey, you seem to know about studying the colours, I have learnt all the colours of the 6 metal aqua ions, but question, do we need to know all the Mn and V?

Cheers Yeh I sort of cheated and just learnt the ones that change lol, but the colour really confuse me..I keep forgetting them, I think I'll try doing your method and see if it works..hopefully just hopefully it will.. ;D Also, for Al with xs NaOH, is it [Al(OH)4(H20)2]- or something else? The mark scheme say something different and I have this written down :/ What work are you doing now? Reckon it'll all be done by 1??

No need to know them.

Anyone? Do we need to know Mn and V colours for the individual oxidation states?

Why are some electron affinity endo and some exo?

I did the jan11 a few weeks ago, not properly, just did a q, marked it, then the next as I had soo much other stuff to do and now have forgotten about it all Btw can you help me with q 8c from the jan10 paper? I don't know which equations to use to see the ratio of the moles :/

The titrations are annoying, I can do them but never know what to do for the last step when it wants the percentage or something...

And I've just remembered that I still need to go through mod1 after I've been thorugh the syllabus

I hope it's done by 1. I'm going to make sure I don't fall asleep. I'm gonna go over the 3 past papers. Then go over content once more because I'm very sure I've forgotten it all. It's so hard to remember these random random randommm bits of information.

I'm getting tired.

1st