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ocr a f325 revision thread

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Reply 3140

DudeBoy

Original post by kuku2013

hey guys what do we need to know about hexadentate ligand (EDTA)

6 co-ordinate bonds, used to cure metal poisoning. Very stable and very high Kstab

Reply 3141

kuku2013

Original post by DudeBoy

6 co-ordinate bonds, used to cure metal poisoning. Very stable and very high Kstab

thanks do we need to know how it bond to metal ion

Reply 3142

rival_

Original post by DudeBoy

So first do 10^-pH to find [H+]
=2.2387*10^-5
Rearrange the Ka equation to make Ka/[H+]=[A-]/[AH]
So [A-]/[AH]=2.78/1
So you need 2.78 moles of [A-] for every 1 mole of [AH]

I think anyway :s-smilie:

Hmm that might just make more sense :/

Reply 3143

DudeBoy

Original post by kuku2013

thanks do we need to know how it bond to metal ion

We just need to know that 1 EDTA forms all the bonds with a 6 order metal ion, we won't need to draw a diagram :smile:

Reply 3144

otrivine

Original post by AyshaK

equal volumes of water are added but conc stays the same so the overall volume doubles and if they're asking for conc in the overall volume you'll half the conc if that makes sense?

thank you

okay when you say for conc for overall volume? you mean?

Reply 3145

kuku2013

hey is it worth me doing the jan 2013 paper?

Reply 3146

DudeBoy

Original post by kuku2013

hey is it worth me doing the jan 2013 paper?

I don't think it will harm you to be honest :smile:

Reply 3147

narli

Original post by otrivine

thank you

okay when you say for conc for overall volume? you mean?

whats this about?? can you explian

Reply 3148

kuku2013

what do I need to know about stability constants? I know how to work out kstab

Reply 3149

Pride

Original post by _sparks

Yes I understand that.
But to get to the 1st equation FROM the 2nd, why dont we divide by 2, because 2Cu(II) reacts with iodide but the 2Cu(II) is formed from 1Cu(II) from the first equation?
btw thanks for helping me :smile:

To get from 1st from the 2nd you multiply by 2, because I2, not I-, produced from the 2nd reaction goes into the 3rd reaction. So there must have been twice the number of moles of Cu2+ as there were I2.

Reply 3150

Myocardium

Which complex ion is described as elongated octahedral?

Reply 3151

A-New-Start

I just read a few pages back.. you ppl were awake between 12 - 6 am ??

WTF

Reply 3152

DudeBoy

Original post by kuku2013

what do I need to know about stability constants? I know how to work out kstab

How to work it out.
The higher the Kstab the more stable the complex ion.
That Heamoglobin uses ligand substitution to carry oxygen, and that CO has a greater Kstab than O2

Good luck everybody!

Original post by jess_m94

Good luck everybody!

What time is your exam? :smile:

Reply 3155

DudeBoy

Original post by Myocardium

Which complex ion is described as elongated octahedral?

[Cu(H2O)2(NH3)4]+2

Reply 3156

kimsiclez

So any ideas on predictions of what might come up today?

I'm thinking maybe a long buffer question ( :angry:

hate those..) and maybe something on Kstab as I haven't seen that for a while. Also maybe a longer entropy/free-energy calculation question.

Rates as well might be likely to come up; calculating rate equation and orders etc.

I hope there's a nice long Kc question, the one in Jan 13 was a god send. But that last 7-marker? Yeesh. Although highly likely there'll be some form of a titration/redox calculation at the end as there always is!

Please be nice to us OCR!

(edited 10 years ago)

Reply 3157

DudeBoy

Original post by kimsiclez

So any ideas on predictions of what might come up today?

I'm thinking maybe a long buffer question ( :angry:

hate those..) and maybe something on Kstab as I haven't seen that for a while. Also maybe a longer entropy/free-energy calculation question.

I hope there's a nice long Kc question, the one in Jan 13 was a god send. But that last 7-marker? Yeesh. Although highly likely there'll be some form of a titration/redox calculation at the end as there always is!

Please be nice to us OCR!

Catalysts I think and a question on different ligand substituitions, maybe a buffer linking H2CO3