AQA CHEM4 - 13th June 2012
Chemistry exam discussion - share revision tips in preparation for GCSE, A Level and other chemistry exams and discuss how they went afterwards.
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Re: AQA CHEM4 - 13th June 2012Graph show's ph- 13 at beginning, ph-2 at end, this means it goes from alkaline to acid, it tells you that cresol purple goes yellow in acid, and purple in alkaline, this graph is alkaline to acid, therefore purple to yellow.(Original post by rss.914)
why is the answer to question 1bii in the june 11 paper purple to yellow for the colour change?
http://store.aqa.org.uk/qual/gce/pdf...W-QP-JUN11.PDF -
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No you're wrong. I believe that question was referring to why you can't do it in the laboratory - HCN is toxic.(Original post by NightBear)
KCN.
One of the 2010 mark schemes explicitly mentions not to accept HCN; so the book IS right
Either should be fine, chemically.
If you have a quick look in Jan'11 MS pg17 you'll find the used HCN. -
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Re: AQA CHEM4 - 13th June 2012I'd rather stick with KCN seeing as it's accepted on all papers whereas HCN is not accepted on some questions. So, I'm not wrong.(Original post by Doctor.)
No you're wrong. I believe that question was referring to why you can't do it in the laboratory - HCN is toxic.
Either should be fine, chemically.
If you have a quick look in Jan'11 MS pg17 you'll find the used HCN. -
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Re: AQA CHEM4 - 13th June 2012its one of the recent papers i think the jan 2010..(Original post by Doctor.)
HCN is toxic, what paper didn't accept it?
this is because HCN is highly toxic gas.... but than gain it is used in the nucleophilc addtion reaction HCN with dil. H2SO4
on that particular paper and on another paperLast edited by g00d4u; 12-06-2012 at 14:08. -
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Re: AQA CHEM4 - 13th June 2012When you look at curve D you see at the start the pH is 13, which is alkali. Cresol purple colour in alkali is purple, as stated, and yellow in acid, which at the end-point the pH is 2.(Original post by rss.914)
why is the answer to question 1bii in the june 11 paper purple to yellow for the colour change?
http://store.aqa.org.uk/qual/gce/pdf...W-QP-JUN11.PDF -
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Re: AQA CHEM4 - 13th June 2012HCN is the nucleophile! KCN is the reactant use to make the nucleophile! read the question is should be pretty obvious which one you use... e.g. what reagent do you use to convert CH3Cl to CH3CN? KCN is the answer, or e.g. what do you use in the nucleophilic addition reaction to form a hydroxynitrile? HCN!!
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Re: AQA CHEM4 - 13th June 2012thanks this answer is more promising....(Original post by Bubbles94)
HCN is the nucleophile! KCN is the reactant use to make the nucleophile! read the question is should be pretty obvious which one you use... e.g. what reagent do you use to convert CH3Cl to CH3CN? KCN is the answer, or e.g. what do you use in the nucleophilic addition reaction to form a hydroxynitrile? HCN!! -
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Re: AQA CHEM4 - 13th June 2012It's an easy mistake to make in an exam, i did it once so i got it cleared up with my chemistry teacher after CHEM4 in january(Original post by g00d4u)
thanks this answer is more promising....
KCN + HCL -> HCN + KCL
the HCN then dissociates to give the CN nucleophile which then reacts with another species usually by addition reactions.
KCN is not actually the nucleophile, it's the reagent used to make it -
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Re: AQA CHEM4 - 13th June 2012thanks... do we need to know how aspirin is made?(Original post by lamalas600)
Graph show's ph- 13 at beginning, ph-2 at end, this means it goes from alkaline to acid, it tells you that cresol purple goes yellow in acid, and purple in alkaline, this graph is alkaline to acid, therefore purple to yellow. -
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Re: AQA CHEM4 - 13th June 2012No, just the advantages of using ethanoic anhydride over ethanoyl chloride (when making aspirin)(Original post by rss.914)
thanks... do we need to know how aspirin is made? -
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Re: AQA CHEM4 - 13th June 2012sorry for butting into your conversation :P but i doubt that. it's a good example i use to remember how anhydrides can react with carboxylic acids to produce an ester and have beneficial uses other than the fact they are preferred to acyl chloridesbecause they're cheaper and don't release HCl as a product(Original post by rss.914)
thanks... do we need to know how aspirin is made? -
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Re: AQA CHEM4 - 13th June 2012Don't think so, it's just a bit of background knowledge.(Original post by rss.914)
thanks... do we need to know how aspirin is made? -
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Re: AQA CHEM4 - 13th June 2012yes like in the jan 2011 paper Q4f its 3 marks(Original post by Mero8)
Could they ask a big question about chromatography? -
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Re: AQA CHEM4 - 13th June 2012also the last question the step 2 is elimination, the regeants is H2SO4(Original post by g00d4u)
jan 2012 paper questionn 3d
is it ok to write the answer in inoic form :
CH3CH2NH3+Cl
CH3CH2NH2 +HCl -------> CH3CH2NH3+Cl-
please suggest
can we write hot ethanolic with KOH in aqueous ...... -
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Re: AQA CHEM4 - 13th June 2012Can someone Please Help me.
On January 2011,
Question 5i, it says Deduce the number of C-13 NMR Peaks, I don't understand why it is 6, and not 5? Do you include TMS?
Please someone explain:
Link as well : http://postimage.org/image/5ztmsnxm9/
