Edexcel Chemistry Unit 5 June 19 2012

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Reply 160

Moi786

Approximately what are the grade boundaries for an A(raw and UMS)

Reply 161

keerthi3

Do we have to know the reaction of benzene with alkene?

Reply 162

keerthi3

Original post by Moi786

Approximately what are the grade boundaries for an A(raw and UMS)

http://www.edexcel.com/iwantto/Pages/grade-boundaries.aspx

Reply 163

Puloot

Can anyone help me with this question?

Reply 164

keerthi3

I'm using George Facer book to revise and I'm finding loads of extra information that is not in our specification :frown:

Do we need the chemical reactions of phenylamine?

Reply 165

keerthi3

Original post by Puloot

Can anyone help me with this question?

The answer is A
When you consider the reaction of EDTA, you'll find that the moles on the right side more then moles on the left side. Therefore, entropy increases :smile:

Reply 166

natninja

Original post by keerthi3

Do we have to know the reaction of benzene with alkene?

No, at least we've never been taught it and it's not on the syllabus

Reply 167

Belton42

I keep on getting tripped up on questions about hazards because I just don't know which molecules are harmful, which are corrosive and so on. Does anyone know roughly which functional groups tend to be harmful/toxic/corrosive etc? Or even just recommendations as to where I can find this out as my text book doesn't mention it at all. Also for the organic synthesis methods do you think you would still get marks for putting the techniques in the wrong order? Thanks in advance...

Reply 168

marcus94

I keep getting stuck on transition metal reaction You know the reactions between complex ions and ammonia.

When you add ammonia (not excess) is the reaction

[cr(h2o)6]3+ + 3 Nh3 -> [cr(h20)3(OH)3] + 3 Nh4+
OR
[cr(h2o)6]3+ + 3 Nh3 ->[cr(h20)3(nh3)3]3+ + 3H2o

and in excess will it become [cr(oh6)]3- or [cr(nh3)6]3+

Reply 169

keerthi3

Original post by marcus94

Cr3+ with OH-
Blue-purple solution Muddy green precipitate
[Cr(H2O)6]3+ + 3OH- -----> [Cr(H2O)3(OH)3] + 3H2O

Precipitate dissolves in excess to give a green solution
[Cr(H2O)3(OH)3] + 3OH- [Cr(OH)6]3- + 3H2O

With NH3
Blue-purple solution Muddy green precipitate
[Cr(H2O)6]3+ + 3NH3 -----> [Cr(H2O)3(OH)3] + 3NH4+
Precipitate does not dissolve in excess

Reply 170

marcus94

Original post by keerthi3

according to my textbook it does slowly =/
But ok using another example - Nickel for example:
because of adding nh3 its deprotonation so it should be [Ni(h2o)4(OH)2] Right?

but in excess its ligand exchange so would the equation for excess from a little amount be:
[Ni(h20)4(OH)2] + 4Nh3 -> [Ni (h20)2(Nh3)4]2+ + 2oh- + 2h20???

and overall would it be:
[Ni(h20)6]2+ + 4Nh3 -> [Ni (h20)2(Nh3)4]2+ + 4h2o ???

(edited 11 years ago)

Reply 171

Jukeboxing

Original post by keerthi3

Thats strange, after looking through my textbook, it does dissolve in excess NH3

I'll edit the PDF.

Reply 172

Jukeboxing

Sorry for the error, heres the corrected version.

Cr3+ does dissolve in excess NH3

(edited 11 years ago)

Reactions of transition metals (Edited version).pdf188.3KB

Reply 173

Revent

Original post by Backflip

Platinum electrode is used when there are multiple ions in solution in the half cell and also in the standard hydrogen/calomel electrodes.

I believe it is also when one of them is a gas as well. Ie Cl2+2e- -> 2Cl- uses a platinum electrode

Reply 174

marcus94

Original post by Jukeboxing

Sorry for the error, heres the corrected version.

Cr3+ does dissolve in excess

Ah that Pdf is actually really useful, thanks :smile:

just one question: Why is it that most 2+ ions eg cu2+ can bond as [cu(nh3)6]2+ and zinc only bond with 4 ammonia's Ie/ [zn(nh3)4]2+ ??

Reply 175

Backflip

Original post by Revent

I believe it is also when one of them is a gas as well. Ie Cl2+2e- -> 2Cl- uses a platinum electrode

Yeah. Forgot that ^.^

Reply 176

usamakhanlodhi

I'm really running out of time and only have a few hrs to do chem revision?
So q1: what do we need to know about combinatorial chemistry and pharmaceuticals?
Q2: do we need to know the reactions of disposable and rechargable batteries?
Q3: also can things like enthalpy diagrams, hess law stuff come up in this unit because it is synptic?

Reply 177

Jukeboxing

Original post by marcus94

Ah that Pdf is actually really useful, thanks :smile:

just one question: Why is it that most 2+ ions eg cu2+ can bond as [cu(nh3)6]2+ and zinc only bond with 4 ammonia's Ie/ [zn(nh3)4]2+ ??

I'm not sure why, but i think it has something to do with the arrangment of orbitals.

Maybe someone else may know why.

Reply 178

keerthi3

Can someone please reply to this?

I'm using George Facer book to revise and I'm finding loads of extra information that is not in our specification Do we need the chemical reactions of phenylamine?