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Original post by otrivine
the structure is decoloised, (trigonal)planar molecule, the pi orbitals overlap, would include a diagram in the exam, bonding is covalent between carbon atoms, 120 .


I have not yet started chapter 1. When I finished chapter 1 and 2 fully we revise :smile:

Where are you up to now with your revision


its not triagonal planar ? its hexagonal planar
Reply 1441
Original post by jordank123
its not triagonal planar ? its hexagonal planar


Around each carbon atom the bond angles are 120 degrees and the bond shape is trigonal planar.

Benzene itself is a planar molecule with 6 carbons arranged in a hexagonal shape. As you said.


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Reply 1442
Original post by Mus1995
Around each carbon atom the bond angles are 120 degrees and the bond shape is trigonal planar.

Benzene itself is a planar molecule with 6 carbons arranged in a hexagonal shape. As you said.


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Exactly, because around each carbon it is 120 , so the shape is a trigonal planar
Reply 1443
Original post by otrivine
Exactly, because around each carbon it is 120 , so the shape is a trigonal planar


Around each Carbon atom. Not benzene itself. You didn't specify that I think.


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Reply 1444
Original post by Mus1995
Around each Carbon atom. Not benzene itself. You didn't specify that I think.


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I took that from the mark scheme, and they just put , trigonal planar, award 1 mark
Reply 1445
Original post by otrivine
I took that from the mark scheme, and they just put , trigonal planar, award 1 mark


They may do but it is better to know the context and put that in your answer as well. You can't learn the mark scheme and hope to get marks. :P it has the main point you need to write to get the marks. Not the actual whole complete answer.


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Reply 1446
Original post by Mus1995
They may do but it is better to know the context and put that in your answer as well. You can't learn the mark scheme and hope to get marks. :P it has the main point you need to write to get the marks. Not the actual whole complete answer.


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How is revision going :smile:
Reply 1447
Original post by otrivine
How is revision going :smile:


Pretty much done man, only got 3 papers left to do for Tuesday.

Wanna revise? Ask me a question. :smile:


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Reply 1448
Chemistry is wednesday isn't it?

Original post by Mus1995
Pretty much done man, only got 3 papers left to do for Tuesday.

Wanna revise? Ask me a question. :smile:


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Reply 1449
Original post by Dr00n
Chemistry is wednesday isn't it?


Yeah but I'm not doing a paper the day before so Monday** sorry is when I'm gonna have the papers done. :P


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Reply 1450
Original post by Mus1995
Pretty much done man, only got 3 papers left to do for Tuesday.

Wanna revise? Ask me a question. :smile:


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Excellent, very motivated :smile:

Okay , we start from easy ---> hard

1) Describe why triglycerides are insoluble in water (3)
Reply 1451
anyone where, or can make a guess as to where the boundaries for 90UMS lie?
Reply 1452
Original post by otrivine
Excellent, very motivated :smile:

Okay , we start from easy ---> hard

1) Describe why triglycerides are insoluble in water (3)


Triglycerides are not soluble in water because they are non polar molecules. The long chains of fatty acids have many contact points so form many VDW forces as well as decrease the polarity of the compound. Therefore Triglycerides cannot form hydrogen bonds with water, and are insoluble.

Q) When Bromine reacts with Phenol, what observation would you see and what product is formed?


Original post by rosie66
anyone where, or can make a guess as to where the boundaries for 90UMS lie?


60/60 marks.
Reply 1453
Original post by Mus1995
Triglycerides are not soluble in water because they are non polar molecules. The long chains of fatty acids have many contact points so form many VDW forces as well as decrease the polarity of the compound. Therefore Triglycerides cannot form hydrogen bonds with water, and are insoluble.

Q) When Bromine reacts with Phenol, what observation would you see and what product is formed?




60/60 marks.


correct,


orange solution ---> white ppt
Reply 1454
Original post by otrivine
correct,


orange solution ---> white ppt


doesn't the bromine decolourise + white precipitate

EDIT: oh i see you were doing the change from an orange solution, fair dos
(edited 10 years ago)
Reply 1455
Original post by otrivine
correct,


orange solution ---> white ppt

Ohh hello :smile:, ready for the exam?

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Reply 1456
Original post by D4rth
Ohh hello :smile:, ready for the exam?

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Hi how are you :smile:


I think so :smile:


I can no longer say if I am ready for an exam , after the F325 paper in Jan 2013, not sure what to expect
Reply 1457
Original post by Mus1995
Triglycerides are not soluble in water because they are non polar molecules. The long chains of fatty acids have many contact points so form many VDW forces as well as decrease the polarity of the compound. Therefore Triglycerides cannot form hydrogen bonds with water, and are insoluble.

Q) When Bromine reacts with Phenol, what observation would you see and what product is formed?




60/60 marks.


:/ after F325 I need as many as i can get
Reply 1458
überambitious_ox
Hiya,

I read on a thread that you got 144 UMS in the F325 unit. Well done!

Please could you provide me any tips/advice/sources that you used in order to have done so well.

I am aiming for an A*; any advice would be appreciated.

Thanks :smile:


OFcourse, quite simple to get high mark on this exam:
1) do every past paper, under exam conditions, mark critically and analyse paper after so you understand everything on it and would get full marks if you did it again.
2)Do all the relevant legacy papers(If you want A* do all of them)
3) do the stretch and challenge questions on the CD
4)Do all the end of chapter questions
dont do the things in this order though, as long as you are a normal logical person and are not stupid, you should get atleast your 135/144, A* in F325, if you do all of this
Reply 1459
Original post by Mus1995
Triglycerides are not soluble in water because they are non polar molecules. The long chains of fatty acids have many contact points so form many VDW forces as well as decrease the polarity of the compound. Therefore Triglycerides cannot form hydrogen bonds with water, and are insoluble.

Q) When Bromine reacts with Phenol, what observation would you see and what product is formed?




60/60 marks.


brown/orange --> colourless, bromine delcolourises ,

white precipitate 2,4,6-tribromophenol forms and 3HBr,

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