[MrGuillotine]

(Original post by tomsey11)
Thats what my revision guide said too but why is the half cell with the high E value on the left in this question and answer::
(question 3ai june2002):
Au3+| Au = +1.41V
Ag+ | Ag = +0.80V

Make the cell diagram from these 2 half cells, and calculate Ecell

the answer in the MS is...
Au | Au3+ :: Ag+ | Ag

Ecell = 0.80 - 1.41 = -0.61

I would put the Ag cell on the left because it has the lowest E value, and is therefore the oxidising half equation, but thats clearly wrong!!

please help!!

Thanks alot

You know, I dont think its a simple matter of most positive on the right. Look at the Hydrogen cell with any element. Hydrogen always goes on the left, by convention, but you can still get half cells on the right with a less positive (more -ve).

H2 | 2H(+) || Mg(2+) | Mg E = - 2.37

here hydrogen is the more positive one but is on the left.


Edit: Read page 403 of the Student Guide, 3/4 of the way down. Should answer your question.

You could have drawn the Ag on the left ( doesnt matter really ) as long as you get the sign of the cell EMF correct. So with your example, if you did put Ag on the left, the final emf would be +0.61V NOT -0.61V

[tomsey11]

Ahhhhhhh i get it!!

It doesn't matter which way round you write the cell, but the sign of the emf must always be the polarity of the right hand electrode!

thanks alot!!

[eugenius 8]

when doing a born haber cycle, is the 2nd IE value eg. Mg to Mg 2+ include the the first IE value in the databook so you have to add the 2 values together? thanks in advance

[man_in_black]

You have to add them.

I've just found out we need to know about stability constants, yet I don't know a single thing about them. Could someone please tell me what we need to know?

[notransistory]

Add them together.

[pheonixfire]

what does the Rf value show?
i mean i know how to work it out, but no idea what it actually means...

[dhugga]

does anybody have any of the jan papers?

[notransistory]

(Original post by pheonixfire)
what does the Rf value show?
i mean i know how to work it out, but no idea what it actually means...

It's to determine different amino acids. Each amino acid had a different solubulity in the solvent due to varying bonds and elements e.g. hydrogen, sulphur in the R groups and will move a different distance on the chromatogrpahy paper.

[pheonixfire]

so it shows the solubility of the amino acid, which differs for each one?
therefore can determine which one it is...

[kidda_puttar]

(Original post by MrGuillotine)
I had to do a real quick scan, so hope you can read it.

Enjoy! (like you'd enjoy revision )

Thanks for the markscheme...would you mind posting the paper as well? (june 06)

[JoineeMoore]

and Rf is never affected by mass only ever solubility. As for teh stabilitiy its just what it says on the tin how stable the complex ion is. The formula for it is in the book however in the book it is shown as K not K(subscrpt stab). The ligand with a higher stability constant will displace one with a lower stability constant.

[MrGuillotine]

(Original post by dhugga)
does anybody have any of the jan papers?

They dont exist for this module, not for the new syllabus that we're doing anyway.

So its only June 02-06.

I may be able to post the june 06 paper later, but cant promise anything - busy revising.

[kidda_puttar]

(Original post by MrGuillotine)
They dont exist for this module, not for the new syllabus that we're doing anyway.

So its only June 02-06.

I may be able to post the june 06 paper later, but cant promise anything - busy revising.

Would be indebted if you do post june 06

I have 1995-1999 June and Jan if you want (in exchange..)...even though the syllabus is a bit different, the questions are still good practice.

[MrGuillotine]

^They would be useful, if it aint too much trouble. thanks.

Heres your paper:

[Tabris]

How many pages have people tabbed? And, if you can be arsed, which pages did you tab?

[kidda_puttar]

(Original post by MrGuillotine)
^They would be useful, if it aint too much trouble. thanks.

Heres your paper:

Ooo thank you v much. PM'd you.

[tomsey11]

(Original post by Tabris)
How many pages have people tabbed? And, if you can be arsed, which pages did you tab?

I assume ur talking about the data book...

If so i tabbed:
infra-red spec
NMR
Ionization
Bond energies
Element thermochem data
inorganic thermochem data
organic thermochem data
electron affinty +m lattice energy
electrode potentials
Ka

Is anyone tabbing the student book too??

[e_s_emsie]

ive tabbed both although when doing practice papers under 'exam conditions' ive found that my tabs on the course book havent been that useful and is just as easy to look it up in the index. best of luck everyone....nuffield is known for being a v hard chemistry course!!!

[Chiba_Revolution]

That sounds well harsh. Yeah Im franticly (is that how u spell it) revising chemistry today Ive done the specemin paper on the website, but ive not got any other past papers. I was getting 50/60 at the end of school, i hope i havent fogotten too much.
Erm Im going to oxford next yr (wadham college), doing physics. But Im not really geeky.... honest. Where are you going?

Aston to study pharmacy!...you sure your not a geek...?physics + oxford holy!

[Chiba_Revolution]

ive tabbed both although when doing practice papers under 'exam conditions' ive found that my tabs on the course book havent been that useful and is just as easy to look it up in the index. best of luck everyone....nuffield is known for being a v hard chemistry course!!!

Yeap!...why me>? I need an A or am going noweher in fall good thing grade boundaries for syptoic are lower than the other units!