[Next Level]

Guys can anyone help me on q.24 from this paper:

http://www.edexcel.com/migrationdocu...e_20100628.pdf

For (d)(i) I got the mole ratios but why does it mean 2 double bonds are reduced?
For (e) and (f)(i) Just how do you do this? I don't know what's going on in (f)(i)...

Cheers!

[EierVonSatan]

(d)(i) 1 mole of H₂ will reduce 1 mole of double bonds

(e) remember that double bonds reaction with HBr in electrophilic addition reactions

(f)(i) (what does the * denote?) it's an open question - they want you to pick an example, draw the mechanism for your example and explain the stereochemsitry that results

[Next Level]

(Original post by EierVonSatan)
(d)(i) 1 mole of H₂ will reduce 1 mole of double bonds

(e) remember that double bonds reaction with HBr in electrophilic addition reactions

(f)(i) (what does the * denote?) it's an open question - they want you to pick an example, draw the mechanism for your example and explain the stereochemsitry that results

Thanks firstly

Alright I'll have to remember the fact on (d)(i), and for (e) you're right that makes sense, synoptic stuff

For (f)(i) I just don't get the question? I mean, does it have to be to do with carvone?

[EierVonSatan]

(Original post by Next Level)
Thanks firstly

Alright I'll have to remember the fact on (d)(i), and for (e) you're right that makes sense, synoptic stuff

For (f)(i) I just don't get the question? I mean, does it have to be to do with carvone?

Nope I don't believe it does have to be related to carvne, confusing isn't it?

[Next Level]

(Original post by EierVonSatan)




Nope I don't believe it does have to be related to carvne, confusing isn't it?

Haha it really is, out of the blue you get a question like that Thanks as always, very helpful! Also would you mind if I asked another quick MCQ question on the same paper, which is q.5 and how do you approach such a q?

[EierVonSatan]

(Original post by Next Level)
Haha it really is, out of the blue you get a question like that Thanks as always, very helpful! Also would you mind if I asked another quick MCQ question on the same paper, which is q.5 and how do you approach such a q?

No worries

One of the hallmarks of transition metals is that they often form several different ions, does that help?

[Next Level]

(Original post by EierVonSatan)
No worries

One of the hallmarks of transition metals is that they often form several different ions, does that help?

Afraid not Care to expand?
The answer is C btw, considering there is only 1 big jump it doesn't make sense to me

[EierVonSatan]

(Original post by Next Level)
Afraid not Care to expand?
The answer is C btw, considering there is only 1 big jump it doesn't make sense to me

Look at A, it only has the chance to form a +1 ion as the second IE is very large.

For B, looks like it would form +2 ions for similar reasons as above.

For C there are no real big gaps until the last IE is displayed, so this has the best chance to form multiple ions so far.

Now D, it's first IE is pretty big as it is - so this won't easily form positive ions.

[oHellno]

(Original post by Next Level)
Afraid not Care to expand?
The answer is C btw, considering there is only 1 big jump it doesn't make sense to me

EierVonSatan is correct and that's the best way to look at it, but we will have the data booklet in the exam, so you can just look in there to confirm (if they give the same values)

[Next Level]

(Original post by EierVonSatan)
Look at A, it only has the chance to form a +1 ion as the second IE is very large.

For B, looks like it would form +2 ions for similar reasons as above.

For C there are no real big gaps until the last IE is displayed, so this has the best chance to form multiple ions so far.

Now D, it's first IE is pretty big as it is - so this won't easily form positive ions.

Why does the fact that A and B can form +1 and +2 respectively mean they cannot be transition elements? And for C since there are no real big gaps until the last IE, how does this make it the best one to form multiple ions?

[Next Level]

(Original post by oHellno)
EierVonSatan is correct and that's the best way to look at it, but we will have the data booklet in the exam, so you can just look in there to confirm (if they give the same values)

haha data book gives Mn!

[oHellno]

(Original post by Next Level)
Why does the fact that A and B can form +1 and +2 respectively mean they cannot be transition elements? And for C since there are no real big gaps until the last IE, how does this make it the best one to form multiple ions?

Electrons in 3d and 4s overlap and are similar in energy which is why transition metals can form so many different ions, the amount of energy needed to lose a different amount of electrons is quite similar.

With A the second ionisation energy is so much higher than the first that it's unlikely that it will form a +2 (which isn't really typical of transition metals) and the same goes for B.

[EierVonSatan]

(Original post by Next Level)
Why does the fact that A and B can form +1 and +2 respectively mean they cannot be transition elements?

Re-read the bit about transition metals being able to form multiple ions.

And for C since there are no real big gaps until the last IE, how does this make it the best one to form multiple ions?

What are the ionisation energies telling you? If gives you information about what levels (shells) the electrons are sitting in. Small gaps mean that losing the next electron is relatively easy (in fact it's hard to prevent it).

If you have a bunch of medium gaps instead, the 'intermediate' ions are stable enough to get noticed/be formed. B will not form a +1 ion for very long before losing another electron to give +2...it's got a huge barrier to get to +3.

[Next Level]

(Original post by EierVonSatan)
Re-read the bit about transition metals being able to form multiple ions.



What are the ionisation energies telling you? If gives you information about what levels (shells) the electrons are sitting in. Small gaps mean that losing the next electron is relatively easy (in fact it's hard to prevent it).

If you have a bunch of medium gaps instead, the 'intermediate' ions are stable enough to get noticed/be formed. B will not form a +1 ion for very long before losing another electron to give +2...it's got a huge barrier to get to +3.

Ah right, so you mean that C has medium gaps which are stable enough to be formed, hence it can form multiple ions?

[EierVonSatan]

(Original post by Next Level)
Ah right, so you mean that C has medium gaps which are stable enough to be formed, hence it can form multiple ions?

That'll do

[Next Level]

(Original post by EierVonSatan)
That'll do

Awesome, finally clocked it