Edexcel Chemistry A2 Unit 5 ~ Wednesday 19th June 2013 (Now Closed) Watch

Poll: How pumped up are you for this exam?-(warning)-(bad jokes arene this poll!)
"Titanium-I'm not going to corrode (even at high temperatures)" (A*) (22)
16.67%
"Benzene's my middle name, give me the paper in a week and I'll ace it!" (A) (27)
20.45%
"Yeah, I'm fairly electrophillic (positively charged) about the exam" (B) (27)
20.45%
"I'm in the middle of the salt bridge, but I will pass-eventually" (C) (21)
15.91%
"I'm feeling rather electroNegative about this exam" (D) (18)
13.64%
"Benzene, what's that?" (E) (6)
4.55%
"Chemistry, what's that?" (F) (11)
8.33%
This discussion is closed.
sounique
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#621
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#621
(Original post by jojo1995)

I think we do I keep breaking you bad news today

For eg cu+ forms cucl2
Whilst cu2+ forms cucl4

The reactions are in the blue edexcel book so I think you gosta know them.

Most of the transition metals fo compumounds w/ 6 h2os

Maximum nh3 is usually 4 so [cu(nh3)4(h20)2]

You don't have to include the h20 here if you don't want to fml I need to revise this stuff
But can't NH3 make 6 ligand bonds with Zn? So isn't the maximum 6?
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sounique
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#622
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#622
(Original post by posthumus)
jojo1995 responded to your copper question (as well as my question) and yes you do have to remember all those reactions unfortunately. This unit has less new organic to remember - but there's a lot of redox/ complex reactions to remember also

Erm I'm not too sure about that Kstab... but its only a very short part of the george facer book there's nothing really to remember Ka (from unit 4)... it's the same thing pretty much.
Someone please enlighten me on what Kstab is?
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sounique
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#623
(Original post by posthumus)
No that is for yield isn't it ?

Don't you get the sensitivity of the pipette then...

sensitivity/reading x 100 = percentage error
So what is the sensitivity of a pipette? It only measures one volume so surely nothing can go wrong there?
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sounique
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#624
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#624
Does anyone know why d-block ions have strong electric fields?
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posthumus
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#625
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(Original post by sounique)
Someone please enlighten me on what Kstab is?
Don't worry too much about it it's in the george facer book... its worked out in exactly the same way as Ka Acid dissociation constant. Except here it's just called K stability constant


(Original post by sounique)
So what is the sensitivity of a pipette? It only measures one volume so surely nothing can go wrong there?
It depends on the pipette, what is the scale on the one you are referring to ?


(Original post by sounique)
Does anyone know why d-block ions have strong electric fields?
I really don't think you need to know this ! Its to do with the way the atoms can allign and also if you want to know specifically within the atom why this is... I'm pretty sure this is learnt at a higher level and involves a bit of quantum mechanics I believe
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sounique
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(Original post by posthumus)
Don't worry too much about it it's in the george facer book... its worked out in exactly the same way as Ka Acid dissociation constant. Except here it's just called K stability constant

It depends on the pipette, what is the scale on the one you are referring to ?

I really don't think you need to know this ! Its to do with the way the atoms can allign and also if you want to know specifically within the atom why this is... I'm pretty sure this is learnt at a higher level and involves a bit of quantum mechanics I believe
So there isn't a possibility they could ask us about Kstab? The Facer book looks really popular on this thread. Am I OK to just be comfortable with the Edexcel textbook?

I'm not too sure, it was an exam question but since they didn't specify a scale is that an indication we don't need to work out its % error?

Oh right! Erm, this sentence is in the Ed book (pg 172) and thought it could be a potential exam question to ask us why they have stronger fields. Never mind, thanks for your replies mate.
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sounique
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On page 174, it seems tetrahedral complexes are formed when the ions have complete d orbitals whereas incomplete d orbitals produce square planar? I swear Co is incomplete and in fact all of the are incomplete so can someone please explain what they are trying to say?
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jojo1995
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#628
(Original post by lordmackery)
And do we need to know how to calculate Kstab? It's not in my textbook but it's in my revision guide?? Very confused.
no you don't need to know how to do the calulations - you just need to know that its a measure of stability i guess and what a high value means and what a low value means.


(Original post by sounique)
But can't NH3 make 6 ligand bonds with Zn? So isn't the maximum 6?
yeah there are only 4 nh3 ligands attached, you can add on 2 waters to make it up to 6 though... you can leave the waters out if you want ... my teacher taught it to us that way though.

(Original post by sounique)
Someone please enlighten me on what Kstab is?
you don't need to know how to do the calculations ... but yeah its what posthumus said
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jojo1995
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(Original post by sounique)
On page 174, it seems tetrahedral complexes are formed when the ions have complete d orbitals whereas incomplete d orbitals produce square planar? I swear Co is incomplete and in fact all of the are incomplete so can someone please explain what they are trying to say?

when they form bonds with ligands, don't some ligands donate electrons to the ions ? idk - wouldnt that make them full ?
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posthumus
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(Original post by sounique)
So there isn't a possibility they could ask us about Kstab? The Facer book looks really popular on this thread. Am I OK to just be comfortable with the Edexcel textbook?

I'm not too sure, it was an exam question but since they didn't specify a scale is that an indication we don't need to work out its % error?

Oh right! Erm, this sentence is in the Ed book (pg 172) and thought it could be a potential exam question to ask us why they have stronger fields. Never mind, thanks for your replies mate.
It is very popular, and our teacher gets annoyed sometimes because people can get carried away with the unnecessary details You will be fine with the Edexcel book The only thing you may be missing out on is a few worked examples... but you'll do practice questions anyway.

If there is no indication what scale the pipette has then I highly doubt they would ask you to find % error of that specific reading. However it is still possible... For example if they give you readings:
1.82
1.96
1.67

You can assume the sensitivity of the instrument is +-0.01
But I still don't think that is a fair question to ask still since the sensitivity of equipment's can be anything !


Yes it may just mention they have magnetic properties... I mean in the George Facer book it just states that some are ferromagnetic and other paramagnetic and that's it (even that is unnecessary to know)
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sounique
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(Original post by jojo1995)
when they form bonds with ligands, don't some ligands donate electrons to the ions ? idk - wouldnt that make them full ?
Co = [Ar] 4s2, 3d5
Co2+ = [Ar] 4s0, 3d5
when the four lone pairs from let's say the cl- attack, how does that make it full? It fills the d orbital and starts filling the 4p.. Oh so are you saying the d orbitals have to be full?

But even so with [Ni(CN)4]2- the four lone pairs from CN start filling up the d orbitals but that's square planar and the book seems to suggest it has incomplete d orbitals.

so confused
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posthumus
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(Original post by jojo1995)
yeah there are only 4 nh3 ligands attached, you can add on 2 waters to make it up to 6 though... you can leave the waters out if you want ... my teacher taught it to us that way though.
Isn't that only if the H2O is not planar to the complex ion?
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sounique
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(Original post by posthumus)
It is very popular, and our teacher gets annoyed sometimes because people can get carried away with the unnecessary details You will be fine with the Edexcel book The only thing you may be missing out on is a few worked examples... but you'll do practice questions anyway.

If there is no indication what scale the pipette has then I highly doubt they would ask you to find % error of that specific reading. However it is still possible... For example if they give you readings:
1.82
1.96
1.67

You can assume the sensitivity of the instrument is +-0.01
But I still don't think that is a fair question to ask still since the sensitivity of equipment's can be anything !


Yes it may just mention they have magnetic properties... I mean in the George Facer book it just states that some are ferromagnetic and other paramagnetic and that's it (even that is unnecessary to know)

Ahh sweet, thank you!
No, I saw paramagnetic in a mark scheme as an actual answer to a question. Sorry do you mind explaining that to me?

Would you recommend it (would it help my chances of getting an A* in the exam knowing those extra details?) So do you not revise from the Ed book?
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jojo1995
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(Original post by sounique)
Co = [Ar] 4s2, 3d5
Co2+ = [Ar] 4s0, 3d5
when the four lone pairs from let's say the cl- attack, how does that make it full? It fills the d orbital and starts filling the 4p.. Oh so are you saying the d orbitals have to be full?

But even so with [Ni(CN)4]2- the four lone pairs from CN start filling up the d orbitals but that's square planar and the book seems to suggest it has incomplete d orbitals.

so confused
i honestly dont know ... im confused too - i have a chem lesson tommorow so i can ask - no they only fill up the 3d dont they ? why would they fill up the 4p... but the ligands donate electrons to the transition metals dont they- through formation of dative covelant bonds
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jojo1995
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(Original post by posthumus)
Isn't that only if the H2O is not planar to the complex ion?
Doc5.odt

like this ?
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sounique
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(Original post by jojo1995)
i honestly dont know ... im confused too - i have a chem lesson tommorow so i can ask - no they only fill up the 3d dont they ? why would they fill up the 4p... but the ligands donate electrons to the transition metals dont they- through formation of dative covelant bonds
Yes, that would be great! If they only fill up the 3d orbitals that means some are flying around freely!! That's why I assumed the move onto the next energy level. Aren't you on Easter holidays?
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posthumus
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(Original post by jojo1995)
Doc5.odt

like this ?
Yup ! but if the H2Os' were planar to the complex ion, then they have to be included ?
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jojo1995
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(Original post by sounique)
Yes, that would be great! If they only fill up the 3d orbitals that means some are flying around freely!! That's why I assumed the move onto the next energy level. Aren't you on Easter holidays?
yes i am, but we have an easter revision session chemistry is acc so confusing - my head is spinning right now

(Original post by posthumus)
Yup ! but if the H2Os' were planar to the complex ion, then they have to be included ?

yes... but you see in cu(h20)6 - i cant find my square brackets, do excuse me
you would always write cu(h20)6 even though 2 h20s are not planar right ?
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posthumus
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(Original post by sounique)
Ahh sweet, thank you!
No, I saw paramagnetic in a mark scheme as an actual answer to a question. Sorry do you mind explaining that to me?

Would you recommend it (would it help my chances of getting an A* in the exam knowing those extra details?) So do you not revise from the Ed book?
Okay so transitional metal complexes are very slightly magnetic so they lie parallel to a strong magnetic field (caused by the ion having one or more unpaired d-electrons).

I haven't used the edexcel book for over a year! funny enough since I started using it I haven't been doing so well lol But I have an obsession for learning every detail and further

I think it would help if you feel the edexcel book does not explain some things properly to you. I use the edexcel revision guide instead of the actual text book (its brilliant).
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posthumus
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(Original post by jojo1995)
yes i am, but we have an easter revision session chemistry is acc so confusing - my head is spinning right now




yes... but you see in cu(h20)6 - i cant find my square brackets, do excuse me
you would always write cu(h20)6 even though 2 h20s are not planar right ?
No you can write [Cu(H2O)6]^2+ as [Cu(H2O)4]^2+ as well

that's why I was asking
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