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OCR B Salters - F335 Exam - 15 June 2011

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Reply 700
Avatar for jungdao
jungdao
Original post by tom108
So far, about 9 for me. That will soon change....


Do you know how many marks you need on this for the grade you want? I don't think I'm in trouble unless I drop below 75% UMS on this exam.
Reply 701
Avatar for tkoki1993
tkoki1993
OP
10
Original post by ManPowa
Question 1
Organic compound: phenyl amine

Structure: 1,3-dimethly amine

Condition: temperature below 5 degrees (ice-cold)

Reaction mechanism: electrophillic substituition

Witts prediction: Anyone.!

Why dyes are coloured:
electron is excited / jumps up energy levels AND (as a result of) light / (UV) radiation / energy / photons
frequency (absorbed) depends on energy change
OR (?)E = hv
dyes / coloured compounds / ‘compounds containing more benzene rings’ (AW) absorb in the visible / absorb light
plus two from:
energy levels are closer / energy gap is smaller / excitation energy is smaller when there is: more delocalisation more conjugation more than one benzene ring
larger chromophore
(dyes) transmit / reflect (NOT emit) the complementary colour ??


Explain why benzene undergoes substitution: maintain stability, delocalised electrons keep the benzene ring intact and what else??

Total : 16 marks


For witts prediction, I wrote orange is between brown and yellow. and the extent of delocalisation in the dye is between the extent of delocalisation in brown and yellow
Reply 702
Avatar for ManPowa
ManPowa
7
Original post by tom108
I put temp below 5 and alkali conditions.
Didnt the two colours mix to from a orange colour?

For the six marker, that sounds perfect!!

Other answers i remember writing?

Ether
Alkene
Ringing a COOH
The reason we add salts,? So that the molecule is soluble in water.

Can you remmeber Q 2?


Original post by jiemanm10
thanks for the post :smile: could you do this for all the questions please?


Yep in the process and ive done question 2 aswell.. See below :biggrin:
Original post by ManPowa


Comment - If your total entropy was positive, then a fuse will not be required as the reaction is spontaneous. However, if your toral entropy change was negative, then a fuse will be required. I think on the mark scheme, this will be ECF as even if you get the wrong answer but you can still get the mark for the comment.


With this one I think they wanted us to say the total entropy was positive so it should happen 'spontaneously' but just needs a fuse to start it up due to having a high activation enthalpy
(edited 12 years ago)
It's a joke how many marks i lost in this bastard paper :cry2:

DOES ANYONE HAVE A GUESS FOR WHAT THE GRADE BOUNDARIES WILL BE?????
Reply 705
Avatar for jiemanm10
jiemanm10
Original post by ManPowa
Yep in the process and ive done question 2 aswell.. See below :biggrin:


Thank you very much! how can you remember all these questions?!
Reply 706
Avatar for ManPowa
ManPowa
7
Question 3 - 20 marks

molecular formula : C8 H8 02

Equasion: phenylethanoic acid + calcium carbonate >>>> ????

Curly arrow on the retrosynthetic analysis - From the Ch2 to the CO BOND

Explain why synthons are not used to make the required compound.

Nucleophilic substituition : Swap the CN with the Br and then leave the bromine as Br-

Data sheets reageants : H+/H20/ with reflux

Predict: As the forward reaction is exothermic, the equilbrium shifts to the left to absorb the heat and counteract the change. The equilibrium constant Kc, shall decrease..

circled functional group : ether
Functional in IAA BUT NOT IN THE OTHER TWO : Amine

Wavenumber : O-H bond at a peak of 2500 - 3200 cm-1

Circle just the carboxylic acid group.. this is the common pharmacophore in all 3 molecules

Formula of the salt : someone has previously posted the exact answer

Suggest why it is converted into a salt : I put to control the soil pH :/ lol and then i added salts are ionic which are water soluble.. Hmm... Answer people ..!!

2 arguments :
Inexpensive (cheap), use in small concentrations. anything else.. !!!
Reply 707
Avatar for ManPowa
ManPowa
7
Original post by jiemanm10
Thank you very much! how can you remember all these questions?!


I have a ****e memory.. its just that i happen to have the exam in front of me lol
Reply 708
Avatar for HK11
HK11
Original post by ManPowa
Explain why synthons are not used to make the required compound.


Because they rarely exist, they're just 'idealised' fragments
Reply 709
Avatar for jimmeh
jimmeh
Original post by jungdao
Flourine is always -1.

It was 3S + 2CuF2 --> 2CuS + SF4 I think.

We were told that copper is +2 to start with.

Sulfur goes from 0 in 3S to +4 in SF4. (oxidation)

Apparently sulfur also gets reduced: 0 to -2 in CuS.

I erroneously wrote copper gets reduced from +2 in CuF2 to -4 in CuS >_> now I think of it, copper can't be a -4 ion so both answers were sulfur. In CuS the states are +2 and -2.


That was a horrible question. There must be so many people (me included) who got that wrong...Only one person I spoke to after the exam got it right.

Overall though, didn't think it was too bad, not an easy paper, but I've done worse. The easy questions seemed really, really easy and the hard questions really, really hard.
Reply 710
Avatar for tom108
tom108
Original post by ManPowa
Question 3 - 20 marks

molecular formula : C8 H8 02

Equasion: phenylethanoic acid + calcium carbonate >>>> ????

Curly arrow on the retrosynthetic analysis - From the Ch2 to the CO BOND

Explain why synthons are not used to make the required compound.

Nucleophilic substituition : Swap the CN with the Br and then leave the bromine as Br-

Data sheets reageants : H+/H20/ with reflux

Predict: As the forward reaction is exothermic, the equilbrium shifts to the left to absorb the heat and counteract the change. The equilibrium constant Kc, shall decrease..

circled functional group : ether
Functional in IAA BUT NOT IN THE OTHER TWO : Amine

Wavenumber : O-H bond at a peak of 2500 - 3200 cm-1

Circle just the carboxylic acid group.. this is the common pharmacophore in all 3 molecules

Formula of the salt : someone has previously posted the exact answer

Suggest why it is converted into a salt : I put to control the soil pH :/ lol and then i added salts are ionic which are water soluble.. Hmm... Answer people ..!!

2 arguments :
Inexpensive (cheap), use in small concentrations. anything else.. !!!


For the wave number one i put c=o at 1750???
Reply 711
Avatar for peri93
peri93
2
Original post by ManPowa
I have a ****e memory.. its just that i happen to have the exam in front of me lol


hey could u please include the marks for each part of the questions. thanks!
Reply 712
Avatar for dan1993
dan1993
Original post by tom108
For the wave number one i put c=o at 1750???


i think it asked for an absorption above 1750
sorry mate
Reply 713
Avatar for tom108
tom108
Original post by dan1993
i think it asked for an absorption above 1750
sorry mate


I thought it was above 1700cm-1 they said??? :frown:(((
Original post by dan1993
i think it asked for an absorption above 1750
sorry mate


It was above 1700. So that corresponded to the C=O on the carboxylic group
Reply 715
Avatar for lily92
lily92
It asked above 1700..
Reply 716
Avatar for dan1993
dan1993
Original post by tom108
I thought it was above 1700cm-1 they said??? :frown:(((


my bad i could have been over 1700....i just remember 17 something :colondollar:
Reply 717
Avatar for tom108
tom108
Original post by dan1993
my bad i could have been over 1700....i just remember 17 something :colondollar:


haha
Reply 718
Avatar for bala123
bala123
Anyone have an unofficial mark scheme? If you do please let me know thx :biggrin:
Reply 719
Avatar for Boo!xx
Boo!xx
9
Original post by tom108
I thought it was above 1700cm-1 they said??? :frown:(((


it was :]

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