ocr a f325 revision thread

Has anyone got the f325 jan 2013 paper? It would be such a great help for anyone to send me it

hey how are you

up for some revision

Do you know the answer to the question? Balancing redox equations?

yep I do

Right cool. If you're not going to tell me I don't see why you replied.

Anyone else ? Please look above and provide any help if you can.

Would really appreciate it. Balancing REDOX EQUATIONS not too sure about when to use H20 or H+/OH- the book doesn't clarify.

Right cool. If you're not going to tell me I don't see why you replied.

Anyone else ? Please look above and provide any help if you can.

Would really appreciate it. Balancing REDOX EQUATIONS not too sure about when to use H20 or H+/OH- the book doesn't clarify.

Sorry cant revise otrivine, but was just skimming through this thread

Basically if you have more oxygens on the left of the equation then on the left you pretty much always add a H2O to the right hand side, so that you'be balance the number of O. Then to balance Hydrogens you add H+ to the left hand side.

I don't suppose anyone would be able to explain how you're able to work out how many ligands a complex ion will have in it and what all the different colour changes will be as we basically got told in lesson that if in doubt just put 6 around and go from there but that's hardly accurate enough for me to accept.


Posted from TSR Mobile

Hi BUDDY how are you, want to revise

I don't suppose anyone would be able to explain how you're able to work out how many ligands a complex ion will have in it and what all the different colour changes will be as we basically got told in lesson that if in doubt just put 6 around and go from there but that's hardly accurate enough for me to accept.


Posted from TSR Mobile

Regarding the colours, you need to learn all of them by heart.
Secondly, the number of ligands, you just count them in the structure to see how many there are, for example in [Cu(h2o)6]2+ there are 6 ligands and hence, 6 coordinate bonds(dative covalent)

I understand all that, it's just the fact when you react them with something else and the ligand changes too, would they provide us with the equation so we would know how many coordinate bonds there should be, or are we just meant to know those aswell?


Posted from TSR Mobile

do you have an example, of this case, it would be easier to explain to you

Erm it's hard to think of an example as the teacher was just rambling on about it but we reacted copper (II) with ammonia and cobalt (II) with HCL although I'm not sure those are cases where the number of coordinate bonds changes but he did say, if in doubt just go with 6 which won't always be correct so I just want to understand an actual process of working it out in each case.


Posted from TSR Mobile

Ok, so, I presume you know the equations , yes your teacher is correct, because it is 6 coordinate bonds!

But will there ever be a situation where you start with 6 coordinate bonds and after reacting with a solution will change the number of coordinate bonds, maybe reduce it to 4?


Posted from TSR Mobile

yes this is the case when copper(II) reacts with the concentrated HCL

so when [Cu(h2o)6] gives [Cucl4]2-

coordinate number changes from 6 to 4

Okay but would they just expect you to know that or would they provide you with an equation so you're able to work it out for yourself?


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