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.
Hellz_Bellz!
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#1701
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#1701
(Original post by AtomicMan)
Yes

And also, does anyone know whether the dyes are precipitates, or solutions when the products are formed from coupling reaction?
They're precipitates.
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Hellz_Bellz!
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#1702
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#1702
(Original post by James A)
Yep, learn all of that, it's a synoptic paper after all
*cries*

Looks like I'm gonna be up all night.
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Jassstewart
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#1703
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#1703
Why doesn't benzene have double bonds like alkenes?
I know it's a basic question but I can't find a simple answer to it.
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F1's Finest
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#1704
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#1704
(Original post by Jassstewart)
Why doesn't benzene have double bonds like alkenes?
I know it's a basic question but I can't find a simple answer to it.
Because benzene contains a delocalised ring of electrons!

If benzene had double bonds, it wouldn't be called benzene, it would be called Cyclohexatriene
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Bubble734
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#1705
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#1705
(Original post by Jassstewart)
Why doesn't benzene have double bonds like alkenes?
I know it's a basic question but I can't find a simple answer to it.
The pi electron system is delocalised. So every carbon has 4 electrons in its outer shells used for bonding and one of these per carbon in the benzene ring is delocalised (of the other 3, 2 are bonded to neighbouring carbons and 1 to a hydrogen.) So it doesn't have double bonds, doesn't decolourise bromine water etc.

Hope that makes sense I'm pretty sure it's right...
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xampiiexx
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#1706
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#1706
does anyone has access to the specimen paper? also any predictions for tomorrow?
i really need a B in this exam and i just don't think its going to happen, the exams are so fudging hard i keep getting high C's/low B's in the past papers :/
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posthumus
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#1707
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#1707
(Original post by Bubble734)
I'm stuck on this question too but still don't understand- why did you write the Cl outside of the square brackets? Are the Cl ions bonded to the chromium at this point?
Anyone?!
Thanks
Ionic bonding instead of dative


(Original post by 994)
why is methylamine a stronger base than ammonia?
Methyl group pushed electrons towards nitrogen make it more delta negative... & hence it will become a stronger base
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Bubble734
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#1708
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#1708
(Original post by xampiiexx)
does anyone has access to the specimen paper? also any predictions for tomorrow?
i really need a B in this exam and i just don't think its going to happen, the exams are so fudging hard i keep getting high C's/low B's in the past papers :/
I have a prediction- my teacher said to prepare for one of those questions that are normally in unit 4 (but wasn't this time) where they give you an NMR and other info and have to work out the structure of a molecule. But who knows really..
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posthumus
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#1709
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#1709
Does anyone else find those "Big jumps" in successive ionisation energy questions... hard to spot?

What would you guys recommend Should I actually find the different between all the values
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Bubble734
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#1710
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#1710
(Original post by posthumus)
Does anyone else find those "Big jumps" in successive ionisation energy questions... hard to spot?

What would you guys recommend Should I actually find the different between all the values
Yeah I think they're really hard to spot! What I found easier was to write them down as smaller numbers so instead of 496, 4563, 6913, 9544, 13352 I wrote 5, 45, 69, 95, 133 and it just seemed easier to spot jumps with smaller numbers.
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Chqr
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#1711
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#1711
Do we need to know the Chemistry of Chromium (as in Colours, reactants and formation of dichromate ions) for all the transition metals?
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Jassstewart
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#1712
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#1712
Can someone explain how to reduce an aromatic nitro-compound to form an Aryl Amine pleaseeeeeeeeee
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bubblegummer
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#1713
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#1713
(Original post by posthumus)
Only has one oxidizing state... forms 1 ion only, Sc3+

Transition metals have partially filled d orbitals in their ions
Thank you

(Original post by clydeshen411)
It only forms 1 ion which is Sc3+, empty d orbitals as all electrons in 4S and 3d are removed.
Thank you
(Original post by GeorgeL3)
A transition metal is any element that can form a stable ion with an incomplete d-orbital (but still partially filled).

Since Scandium's only stable ion is the +3 ion this means that it will have no electrons at all in the d-orbital and so doesn't fit the definition of a transition metal.
Thank you Your notes are really amazing!! I greatly appreciate that

(Original post by orange94)
Lol is this really a question. Pretty standard stuff.


First if all you have to understand what the definition of a transition metal is




A transition metal is one which forms one or more stable ions which have incompletely filled d orbitals.




Sc as an ion is sc3+ which has an empty d- orbital!


You must remember that it had the electronic configuration [Ar] 3d1 4s2


When it loses its 3electrons it's left with [Ar]


Get it now ?? Looool




Posted from TSR Mobile
Thank you. I asked just to be sure. You're a genius
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xampiiexx
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#1714
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#1714
(Original post by Bubble734)
I have a prediction- my teacher said to prepare for one of those questions that are normally in unit 4 (but wasn't this time) where they give you an NMR and other info and have to work out the structure of a molecule. But who knows really..
i hope so i'm really good at those
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Piravinthan
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#1715
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#1715
chemistry unit 5 edexcel june 2010 mcq 5
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Jassstewart
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#1716
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#1716
(Original post by 994)
why is methylamine a stronger base than ammonia?
It's because election from the alkyl group increases the electron density meaning that the nitrogen atom can hold a proton better/ more strongly that NH3
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F1's Finest
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#1717
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#1717
(Original post by Jassstewart)
Can someone explain how to reduce an aromatic nitro-compound to form an Aryl Amine pleaseeeeeeeeee
Tin and Concentrated HCl. Heat under reflux. Once carried out, add NaOH and you then have to obtain the phenylamine by steam distillation.
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posthumus
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#1718
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#1718
(Original post by Bubble734)
Yeah I think they're really hard to spot! What I found easier was to write them down as smaller numbers so instead of 496, 4563, 6913, 9544, 13352 I wrote 5, 45, 69, 95, 133 and it just seemed easier to spot jumps with smaller numbers.
I really like that idea, thanks !

Will rep you later, I ran out for the day
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posthumus
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#1719
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#1719
Anyone else revising on here throughout the night?

I'm going to go sleep now
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Mallika
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#1720
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#1720
(Original post by Qwob)
Chiral means a non-superimposable mirror image. A good analogy is our hands, they are both identical but cannot be superposed, because of the position of the thumb.

In chemistry, it's the same principle but we use it when talking about molecules and isomers. A chiral centre means an atom (carbon) that has 4 different groups attached to it. This makes the molecule chiral because the groups can be attached onto the carbon in different ways, producing two enantoimers (or optical isomers).

Here's an example of an amino acid with 4 different groups attached to a central carbon atom, making it chiral:

thank you repped Is there a specific definition we need to know though? I think it's come up in unit 4, but I didn't get it back then :P
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