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Never mind, I goddit.
(edited 9 years ago)
Original post by spleenharvester
Hahahaha this question from June 2012:



Answer: http://i.imgur.com/Qoq1BlP.png

The deduction of ester/no OH group was easy enough but I literally could not have pulled those structures out of my ass if I tried. How are we supposed to figure those out!

Feeling mega confident for this exam but some of these questions are just on a whole new level :tongue:


That question was bs

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Original post by The_Blade
That question was bs

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I think for questions like that we literally just have to expect to draw some really wacky ****.

I guess the clue in e) was the formula doubling minus H2O and in f) was the acid anhydride + C2H2 (or whatever it was).
Someone explain this iodine numbers thingy pls

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Reply 64
Can anyone tell me if i need to know the nitrogen cycle cos i have never seen it come up once?
Reply 65
Original post by an100
what does it mean by 'alternate' C=C bonds?, does anyone know, please explain, thanks


Alternative C=C bonds ….i think your talking about a conjugate system

Coloured compounds (organic) normally contain unsaturated groups and these unsaturated groups are part of a extended delocalised system (also known as conjugation) in a chromophore which causes change in colour

Examples are -N=N- or -C=C- or -C=O-

if you want to know more just ask.
Original post by jack002
Can anyone tell me if i need to know the nitrogen cycle cos i have never seen it come up once?


When did it come up?

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Reply 67
Original post by jack002
Alternative C=C bonds ….i think your talking about a conjugate system

Coloured compounds (organic) normally contain unsaturated groups and these unsaturated groups are part of a extended delocalised system (also known as conjugation) in a chromophore which causes change in colour

Examples are -N=N- or -C=C- or -C=O-

if you want to know more just ask.


thank you, I was just doing a past paper and in mark scheme it said use the word 'alternative' C=C bonds rather than just C=C to get the mark, so I was thinking what is the difference between the two! in revision guide it saying a'alternative' C-C (single) bonds are also part of conjugated system so I got confused?!
(edited 9 years ago)
Reply 68
Original post by Branny101
When did it come up?

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It hasn't come up just related things to it but I'm just asking if we need to know the formulas for the nitrogen cycle as i haven't learnt them and there like 9 equations to learn for the nitrogen cycle.
Reply 69
Original post by an100
thank you, I was just doing a past paper and in mark scheme it said use the word 'alternative' C=C bonds rather than just C=C to get the mark, so I was thinking what is the difference between the two! in revision guide it saying a'alternative' C-C (single) bonds are also part of conjugated system so I got confused?!


Just write alternative double and single bonds forming a conjugate system/extended delocalised system and I'm sure you'll get the marks but yehhh always write alternative!
Reply 70
Are most of the questions that come every year repeated from past years just phased differently????
Original post by jack002
It hasn't come up just related things to it but I'm just asking if we need to know the formulas for the nitrogen cycle as i haven't learnt them and there like 9 equations to learn for the nitrogen cycle.


I think its more of being able to balance the half equations and write the overall equation as well as being able to systematically name the ions or compounds and draw their structures.

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predictions?
Could someone solve this, the mark scheme doesnt explain it all that well =/

20cm3 of 0.015 mol dm-3 of HNO3 are mixed with 10cm3 of 0.015 mol dm-3 of NaOH.

Calculate the pH of the resulting solution
Original post by YouKnowMyName
Could someone solve this, the mark scheme doesnt explain it all that well =/

20cm3 of 0.015 mol dm-3 of HNO3 are mixed with 10cm3 of 0.015 mol dm-3 of NaOH.

Calculate the pH of the resulting solution


heya,

you cannot work this out unless you have the Ka value

basically Ka= [H+] x [salt]/[acid]

0.015 in 1000cm3 hence mol dm-3

therefore if 0.015 mol in 1000cm3 of HNO3
there will be 0.015/1000*20 in 20cm3 which is 0.0003 mol

then 0.015 mol in 1000cm3 of NaOH
there will be 0.015/1000*10 in 10cm3 which is 0.00015 mol

ka = [H+] * [0.00015]/[0.0003]

we need Ka in order to calculate the conc of H+ and hence the pH!!!
what type of 6 markers are there?
Can someone please upload the f334 and f335 june 2013?

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Original post by parisandrome
heya,

you cannot work this out unless you have the Ka value

basically Ka= [H+] x [salt]/[acid]

0.015 in 1000cm3 hence mol dm-3

therefore if 0.015 mol in 1000cm3 of HNO3
there will be 0.015/1000*20 in 20cm3 which is 0.0003 mol

then 0.015 mol in 1000cm3 of NaOH
there will be 0.015/1000*10 in 10cm3 which is 0.00015 mol

ka = [H+] * [0.00015]/[0.0003]

we need Ka in order to calculate the conc of H+ and hence the pH!!!


It is question 4v in Jan 2013 , it doesnt say anything about Ka =/
Original post by YouKnowMyName
It is question 4v in Jan 2013 , it doesnt say anything about Ka =/


i really dont understand that!
i keep getting the 2.12 answer which only gets you one mark out of the two marks available :confused::eek::s-smilie:
could someone help me with the BOS process?

What do we need to learn? :frown:

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