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Does anyone want to dicuss on Chemistry 5, EDEXCEL paper?

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~Adel~

Are you sitting for three units this time?? That's intense! The practical exam was quite smooth, for me at least and most of my friends didn't find it hard too so synoptic shouldn't make that much of a difference.

I made lots of mistakes in C4 instead of Unit 5 of Biology..so i totally understand how it feels when you realised you did a careless mistake, i felt like smashing my head against the wall.(this is not just an expression, i really felt like doing so..)

I didn't know how to do the kinetics question so i made a rough calculation of the amount of marks that i'm going to lose..that's why i can remember the marks for those questions clearly. ^^

Kiz, your method sounds right to me even though i didn't sit for unit 5 but converting nitrile to carboxylic acid with the use of HCl is correct.(acid hydrolysis)

Yeah, I'm sitting all units 4, 5 and 6 in this exam session - my school didn't let us sit Jan exams for Chem. We do coursework though (centre-conducted practicals throughout the year basically), which was a pain during the year but takes some pressure off because I did well.

I just realised I messed up the calculation at the end (I don't know WHAT I was doing - I divided instead of multiplying by 2. What a pillock) and I forgot that the lone pair was on the N in the N==N geometric isomerism question. My carbocation answer was incredibly dodgy too. And I probably lost all 6 marks on the kinetics question by the sounds of it. So that's potentially about 10 marks gone without going into the pickiness of the mark scheme, other stupid errors etc. I've been brooding on this way too much since Thursday because the amount of careless errors were unbelievable. It wasn't even that I didn't understand it (well, that too) but just silly, silly mistakes. And I need an A in Chem. Ahhh!

Unit 4 was unproblematic though (well, hopefully) and I'm *hoping* the synoptic would be alright.

Did you do Edexcel bio 5 yesterday? How did you find it?

Reply 61

~Adel~

I didn't get the point on the lone pairs for geometric isomerism too..and i didn't really know what i was writing for the carbocation question..what was the difference? I was thinking it could just be..like, the side chain being attached to a different carbon atom and hence the difference..lol..considering all that i've lost 10 marks without going into detail too.

I didn't sit for Unit 4 but i heard it wasn't extremely tough..Bio 5 was..OKish..there's a discussion thread somewhere and i THINK i got most of the things right..but the last question was quite ambiguous as we don't know how many points did they want, i wrote three only, with elaboration but some said we have to write 6..

The rest weren't that demanding..but the bird species question kind of tricked me as i didn't compare the numbers of bird species over the four years and only stated the mean numbers of them.(no one else used that..). The insulin question was another obscure question..i didn't mention a thing on how point mutation alters the insulin as it was already stated in the introduction but someone did and to think of it now, i regret not writing it.

Regarding the calculation bit of Chem 5, the final answer should probably constitute one mark, and perhaps another mark for finding the amount of Cr atoms. So just to put you at ease, you will(at most)lose 2 out of 5 marks.

Looking at your sig..you seem to be taking quite a few subjects for A level!!!

Reply 62

FFCrusader

~Adel~

lol I spent a bit of time looking at the N=N bond thing, thinking....its the same on each side...then for some reason lone pair appeared in my head lol...

about the carbocation, i knew the secondary carbocation is more stable than the primary one, so i just guessed that the primary carbocation broke down and reformed as the secondary one... not 100% sure about that though

i thought it was an alright paper though :smile:

unit 5 biology was...weird but alright lol

Reply 63

Vikid

FFCrusader

lol I spent a bit of time looking at the N=N bond thing, thinking....its the same on each side...then for some reason lone pair appeared in my head lol...

So is it not because the double bond restricts rotation

Reply 64

Rags241

why is it then that N=N bonds have geometric isomerism? I said restricted rotation around the bond, is this right?

Reply 65

Excalibur

~Adel~

Haha, for the carbocation one I rambled on about secondary being more stable due to the alkyl groups etc and so the primary carbocation reforms into the secondary. No idea how it's going to just spontaneously change shape but who cares, lol. I think I should be able to get all the method marks up till the end for the final calculation, as I'm sure I did the rest correctly... it's just the stupid dividing by two! Argh.

I thought Bio Unit 5 went well when I came out of the exam room, but discussing it with people it seems that I may have worded some of my answers badly, and the questions were stupidly ambiguous (the last lipid question - I only wrote down three & elaborated on those only, because it said three in bold. If they wanted three each for plants & animals I'm sure they'd have written each and put it in bold!). I'm not as worried for Bio though because I've already sat Unit 4 in Jan and have coursework so have a bit bigger error margin.

Well, I did A-level Maths last year, Japanese is mother tongue, and my German exams have finished now - so I'm only in effect studying for Bio & Chem. :p:

Reply 66

FFCrusader

Vikid

So is it not because the double bond restricts rotation

well it is that and the fact that there are lone pairs on each N atom, each one acting like a different group on each one

R R
\ /
N=N
/ \
LP LP

like that or something :smile:

EDIT : meh that drawing doesnt come out right but i hope you can work out what i mean lol

Reply 67

~Adel~

I think i got the rhodopsin's question wrong..i didn't mention anything about the splitting of opsin and retinal..didn't revise for that..eek!

Reply 68

kiz_m

Yep i said you can only measure a potential difference...

Erm the phenylamine one i said sodium nitrite and dil HCl

The catalyst i said was AlBr3 but there are other possibilities such as FeBr3 etc.

Erm it needs to be maintained above 0 otherwise the reaction is too slow and below 10 as the diazonium ion decomposes ...(at a higher temp)

Reply 69

IChem

ps7

yay i said the exact same thing as you
apart from i think i wrote sodium nitrate-but i wrote it in a way that it could look like nitrate or nitrate as my handwriting is awful! i wrote conc hcl tho :s-smilie:

and i wrote the same thing about it decomposing or being too sloow

Unfortunately if the examiner deems that an answer you have written is ambiguous, you generally don't get the mark. (Or that's what I've always been told!)

Reply 70

sabinahano

what was the answer for the rates...everyone i know is split on a possible 3 answers... first n first, first n second or second n first

Reply 71

artemisblack

I think I have done OK on these paper- touch wood- but I can honestly say that it is because I did Chemistry after C4(edexcel too) and I royally messed that up- I can forget about an A in maths now- despite having been predicted that!!- My chances of getting the grades for Medicine this year- are looking slimmer by the day :cry:

Reply 72

Tinny

My chances of getting the grades for Medicine this year- are looking slimmer by the day

I know I am so worried about this...I mean to get so far in getting an one offer and everything, just to not make the grades will prob kill me!
Did you get an offer this year?

Reply 73

artemisblack

Tinny

I know I am so worried about this...I mean to get so far in getting an one offer and everything, just to not make the grades will prob kill me!
Did you get an offer this year?

Yep- sorry to reply so late- I got an AAB offer including Chemistry from Keele- and I honestly thought I wasn't going to get anything this year- now that I did- if I mess up- it'll be so much harder to deal with!!! What about you?

Reply 74

Medicine Man

does any one know where i can get the units 4 and 5 papers and the synoptic papers for june 2008?
thanks

Reply 75

aster100

Medicine Man

does any one know where i can get the units 4 and 5 papers and the synoptic papers for june 2008?
thanks

Yes. You're lazy; I've seen each one being posted at least 3 times on various threads. If you're that desparate PM me or something, I'll send you the links.