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Edexcel A2 Chemistry Unit 5 (CH05) - 24 June 2011

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Reply 1780

guitarmike456

Original post by lpmad

Has anyone ogt any e cell questions by any chance?

Post 1106 http://www.thestudentroom.co.uk/showthread.php?t=1320425&page=56

Reply 1781

humz2

Original post by lewieh

what do we have to learn in chormotography? on the cgp it just mentions that paragraph on how to find amino acids ( dip in solvent , spray with ninhydrin etc) that didn't seem that bad? or is there more..

If there are 2 amino acids that travel the same distance on the paper ( it will basically be a big spot as opposed to a standard sized spot) then you have to somehow seperate these

This can be down by rotating the paper 90degrees and using the big spot as the refernce line and also using a different solvent..and then this big spot will chromotographe into 2 spots

and thats it i guess

Reply 1782

sherlllll

Original post by lewieh

I think you need to be able to find the Rf values for amino acids too, to distinguish between them in a mixture of amino acids.

I don't think it is that hard though considering you only have to remember that the Rf value is simply the distance that the amino acid travels from the original line divided by the distance that the solvent travels from the same original line. The Rf values then can be compared to a table to distinguish particular amino acids.

Yeah, ninhydrin spray reacts with the amino acids to produce ammonia, aldehydes, carbon dioxide and hydrindantin. Hydrindantin reacts with the ammonia to produce Ruhemann's Purple, the purple colour seen.

I hope that you only need to know the colour change and not describe the actual ninhydrin reaction :biggrin:

, but yeah that's about it.

Reply 1783

Jabbo12

Original post by imaam

Wow i hope tomorrow's grade boundaries will be like jan 2011's and nowhere near june 2010's (for an A*)!!

But then the exam's got to be as hard as jan 2011. you don't want that to happen.

Reply 1784

tehsponge

Original post by heapatep5

omg a C in june was an A in jan?! WTF :eek:

PLEASE BE LIKE THAT
June was soo much easier aswell. Also sucks how the grade boundaries are sooo tight

I found June so much harder than Jan :lolwut:

Reply 1785

sherlllll

Has anybody got any random benzene/amine/amide questions, or perhaps any organic synthesis questions available? :smile:

. Any at all would be much appreciated.

Reply 1786

guitarmike456

I have a negative feeling about this exam and I'm unsure how feasible it is for me to get my A*.
Oh well hopefully the conditions will be favourable :biggrin:

Reply 1787

memomemootoo

Original post by guitarmike456

I have a negative feeling about this exam and I'm unsure how feasible it is for me to get my A*.
Oh well hopefully the conditions will be favourable :biggrin:

clever

okies good luck people... i'm giving up on chemistry revision now

Reply 1788

antonfigo

Original post by guitarmike456

I have a negative feeling about this exam and I'm unsure how feasible it is for me to get my A*.
Oh well hopefully the conditions will be favourable :biggrin:

Don't worry....getting A*s are really easy nowadays.... good luck..

Reply 1789

abuelzouz

am too scared :frown:

i dont feel that confident..... many euqations many conditions many colours many everything!!!!!

(edited 12 years ago)

Reply 1790

humz2

Original post by guitarmike456

I have a negative feeling about this exam and I'm unsure how feasible it is for me to get my A*.
Oh well hopefully the conditions will be favourable :biggrin:

I actually LOL'ed :redface:

revision must be getting to me

Reply 1791

Choca Mocha

Original post by tehsponge

I found June so much harder than Jan :lolwut:

Me too!

Reply 1792

bitterflew

good luck people :smile:

~10 hour to go :smile:

Reply 1793

TheSingingMute

Original post by sherlllll

Has anybody got any random benzene/amine/amide questions, or perhaps any organic synthesis questions available? :smile:

. Any at all would be much appreciated.

Double check my reaction process if you want ;p

Benzene + HNO3 --H2S04/55°C--> Nitrobenzene --Sn/HCl/heat--> Phenylamine + NaNO2 + HCl --5°C--> Benzenediazonium chloride + Phenol --alkaline solution/cold--> ORANGE AZO DYE

I'm not sure about the phenylamine + nano2 + hcl bit though

(edited 12 years ago)

Reply 1794

sherlllll

Original post by TheSingingMute

Double check my reaction process if you want ;p

Benzene + HNO3 --H2S04/55°C--> Nitrobenzene --Sn/HCl/heat--> Phenylamine + NaNO2 + HCl --5°C--> Benzenediazonium chloride + Phenol --cold--> ORANGE AZO DYE

I'm not sure about the phenylamine + nano2 + hcl bit though

I do believe you are entirely right.

Nitrous acid should be made "in situ" so yeah sodium nitrite should be reacted with HCl at low temperatures to prevent the formation of a phenol.

NaNO2 + HCl ----> HNO2 + NaCl

Thanks :smile:

Reply 1795

Stratos

Anyone up for some scriblink revision here's the link;http://scriblink.com/index.jsp?act=phome&roomid=5425&KEY=DB10865365CACF3F2988EE4F1CFE15AE

Reply 1796

fatima00

for chromatography for separation of amino acids,it says
If the initial spot is larger than 2 mm in diameter, then components with similar Rf values may not be resolved because their spots will be so large that they will overlap considerably and may appear to be one large spot.

whts the 'initial spot'?:/

Reply 1797

guitarmike456

Original post by TheSingingMute

Double check my reaction process if you want ;p

Benzene + HNO3 --H2S04/55°C--> Nitrobenzene --Sn/HCl/heat--> Phenylamine + NaNO2 + HCl --5°C--> Benzenediazonium chloride + Phenol --cold--> ORANGE AZO DYE

I'm not sure about the phenylamine + nano2 + hcl bit though