ALL CIE CHEMISTRY DOUBTS HERE !!

[ahmedigcse4eva]

Hey guys,
Would you please tell me what are the topics in AS chem cambridge, and if there notes for the AS chem.
Thanks alot

[Most UniQue™]

Hey guys,
Would you please tell me what are the topics in AS chem cambridge, and if there notes for the AS chem.
Thanks alot

Here's the syllabus, read it and you'll know what are included:
http://www.cie.org.uk/qualifications/academic/uppersec/alevel/subject?assdef_id=736

And notes, you can find it here:
Notes Here

Notes Here




GOOD LUCK Mate!

[ahmedigcse4eva]

many thaaaaaaaanks 

[MKL]

Hi all, I'm real puzzled by this question from the M/J 2011 paper. Question 29 Paper 12 asks for the change in number of chiral carbons of cholesterol under 1) cold dilute acidified manganate and 2) hot concentrated acidified manganate. I'm pretty sure the answer is +1 and -1 but the mark scheme says it is +2 and -1. Can anyone give me a hand on this?

[Becca]

Hi, @MKL...
It's +2 because the cold dilute acidified KMnO4 produces a diol by adding a hydroxyl group to each of the two carbon atoms in the carbon-carbon double bond within the molecule. This creates two chiral carbon atoms for those two carbon atoms... On the ather hand, when hot concentrated acidified KMnO4 is used, one chiral caron atom is lost because the hydroxyl group within the original cholesterol molecule is oxidised to form a ketone functional group, so the carbon atom attached to that hydroxyl group ceases to be a chiral carbon atom.

Hope you understand my explanation!

Becca

[donhassan]

well here is the question


if we have a cell made up of

AG ion + e=ag   E=0.80v
CU ion + 2 e=cu   E=0.34

if we add water to cu ion/cu beaker and let AG content remain same  will the EMF increase or decrease and WHY ?

[tmisterr]

SInce Ag+/Ag cell has a more positive E value, silver ions will be reduced to silver and copper metal will be oxidized to copper ions. the EMF of the cell (Ered-Eoxd) is therefore 0.8-0.34=0.46v. when you add copper ions, it will dilute the Cu2+/CU cell so from you knowledge of equilibrium (according to that French Guy's Principle, I forget his name lol), this will shift the equilibrium to the left, thus lowering the E value of the cell. so it wil 0.8->0.34=>0.46. As we can see, the EMF of the cell decreases.

[The Golden Girl =D]

According to the 2011 syllabus, you only need to know about the Optical Isomers.

Optical Isomers
When drawing a pair of optical isomers, candidates should indicate the three-dimensional structures
according to the convention used in the example below.
mirror plane

i ain't a CIE Student but can you tell me how to distinguish between Optical Isomers  

EDIT

Thanks =D  

[dlehddud]

They are organic molecules with four different groups attached to the central 'chiral' carbon atom. As you can see in the diagram, the central carbon is attached to a methyl, carboxylic acid, amino group and a hydrogen atom. You are never asked to distinguish which optical isomer rotates light in which direction (optical isomers can alter the plane of light), only to draw the two optical isomers. When in a question, if you're asked to identify a optical isomer or a chiral carbon, just look at a carbon atom that's attached to four different groups. Hope that helped

[The Golden Girl =D]

dlehddud : Thanks mate =D  You helped me get the lesson =D

[The Golden Girl =D]

Here is what I found (Attached)

How can Optical Isomers be separated Chemically?

[dlehddud]

No worries

[dlehddud]

That's hard

[The Golden Girl =D]

I know right , I don't get most of it either -.- 

I don't even think it's in the Syllabus (EDEXCEL)

[dlehddud]

It's not in the CIE syllabus either, so I'm assuming it's not part of any A level curriculum 0.0