[lamalas600]

(Original post by Liyanajamain)
for 7b for "suggest a chemical process that mightve led to contamination of propan-2-ol with propanone" is it okay to say extraction of crude oil?
i wanted to write oxidation but it felt more like a "reaction" than a "chemical process" ? idk

and can someone link me to the revision thread for unit 4 ?

Oxidation is a chemical process


This was posted from The Student Room's iPhone/iPad App

[lamalas600]

(Original post by Picture~Perfect)
A lot of people like to take the time to go over a paper and estimate the grade they might achieve. For me it helps me get closures and allows me to clear my head and move on to other exams. If thats not the kind of person you are then fine, but don't tell other people what they should or shouldn't do. It can be helpful to go over questions from a paper, its nice to find out that you got the same answer as others, it confirms that you were doing the right thing.

^^ I've already said sorry, calm down xD

[Liyanajamain]

(Original post by lamalas600)
Oxidation is a chemical process


This was posted from The Student Room's iPhone/iPad App

do you think 'extraction of crude oil' is too far off? it makes sense to me...

[Baraa3]

(Original post by leah2323)
Well i wrote out an equation like
HX + NaOH goes to XNa + H20

then worked out the moles of HX to be 0.00261
moles of NaOH to be 0.00125
then did 0.00261-0.00125 which gave 0.00136
then used the equation H+ = Ka multiplied by Acid over Salt
which gave me a H+ concentration of 0.000032748 then - logged that and got 4.4848...

arent these values the mole, so how did you put them in the equation, should we not have worked out the concentration in total volume of the acid and the salt, or does the volume cancel out thats why we dont work it out????? :???

[Liyanajamain]

for 4f(i) did anyone get tick blank tick blank? how did you do this quetsion? i did it on the basis that you can only use it for strong bases because the pH scale changes above pH7 so persumably no tailing off beyond that region?

[lamalas600]

(Original post by Liyanajamain)
do you think 'extraction of crude oil' is too far off? it makes sense to me...

I'm not sure... don't think so but I don't have a mark scheme

[Baraa3]

(Original post by Liyanajamain)
for 4f(i) did anyone get tick blank tick blank? how did you do this quetsion? i did it on the basis that you can only use it for strong bases because the pH scale changes above pH7 so persumably no tailing off beyond that region?

yh this is what i did, i hope its correct, the principle is right so yh

[Picture~Perfect]

(Original post by Liyanajamain)
for 4f(i) did anyone get tick blank tick blank? how did you do this quetsion? i did it on the basis that you can only use it for strong bases because the pH scale changes above pH7 so persumably no tailing off beyond that region?

Thats what I did

[Liyanajamain]

what did people get for 4d(i) for the single product?
i was thinking dimethyl ester at first but there would be a hydrogen left so i did an ester group and a carboxylic acid on the benzene

[Liyanajamain]

and a friend wrote the methyl group joining to the oxygen on the molecule so the oxygen is connected to the two carbonyl and also the methyl, forming three bonds. is that possible?

[leah2323]

(Original post by Baraa3)
arent these values the mole, so how did you put them in the equation, should we not have worked out the concentration in total volume of the acid and the salt, or does the volume cancel out thats why we dont work it out????? :???

im sure they cancelled

[leah2323]

hows it 12 peaks

[sconter]

(Original post by lamalas600)
Oxidation is a chemical process


This was posted from The Student Room's iPhone/iPad App

i said it is oxidised, the process is redox..

[purple.piglet]

(Original post by Josh1993)


3 ethyl groups as bonded to N.
c(CH3)3NHCH3

Feel free to amend and add to this as some questions I dont know (only a couple). This is very rushed so likely to be mistakes.

Very very last question - I didn't get this D:

I had N bonded to one hydrogen and two carbons. Then off each carbon I had two CH3 groups and a hydrogen. No idea whether that's right or not! And as you can tell, writing out structural formulae is NOT my forte

[WrongSideUp]

(Original post by lamalas600)
Sorry

don't worry about it

[zoeaw]

(Original post by leah2323)
how's it 12 peaks

Like this (I think)

[Dreams1234]

Does anyone have chem 4 june2012 question paper and mark scheme! Helppp

[rakan95]

(Original post by shuaib786)
yeah i got that as well.

b a
a b
b a

[khalidpatel]

does anyone have a pdf document or work document of every single chem4 mechanism that we gotta draw

[the mezzil]

(Original post by Josh1993)
mol(NaOH) = 10*10^-3(0.125) = 1.25*10^-3
Mol(HX) = 15*10^-3(0.174) = 2.61*10^-3
Mol ( x-) = 1.25*10^-3
mol (HX) after reaction 2.61*10^-3 - 1.25*10^-3 = 1.36*10^-3
[H+] = ka [acid]/ [conjugate base] use mols as volumes cancel
[H+] = (3.01*10^-5) ( 1.36*10^-3 / 1.25*10^-3)
= 3.27*10^-5 moldm^-3

PH = 4.48

For 3) e) I think that is correct.