Chemistry: Post your doubts here!

[MaxStudentALevel]

Could anyone help me with question 7 on ON2012/43 ?? I can't seem to understand how to use the NMR spectra! :/

Here's the link: http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/

Help is needed with the structure if J in the question above please
Also I get solid 80/100 's without revision, I'm pretty much set but I hope no question comes that I'm not able to Attempt !!!

 

[MaxStudentALevel]

Links here: http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/

 

[knowitall10]

thank you. by the way in the examiner report it doesnt show that he divided by 1000 to convert to dm and he used cm..why is that? :/

Maybe because if he had converted it to dm, the values would be too small, and the scale would be "Difficult"- that's precisely that seems to be irritating him in the report , that the scale chosen by candidates was too difficult to interpret. Plus, the mark allocation is not really worth the hard work we have to go through just to get to the retarded values; normally, we only convert to dm3 to show to the examiner that "OMG! I am so damn practical! I totally hate cm3." Maybe te examiner's trying to use a short cut. But what we learn from this is that we do not really have to convert cm3 to dm3 when plotting a graph... hopefully i'm not wrong with my assumption cuz now i'm confused that if such a question does come in the exam, will the examiner accept my conversion or will he suddenly decide to become all "no u have to convert to dm3 or ur gettin a ZERO"?
Hasbuna Allah wa Ni'mal Wakeel!

 

[MaxStudentALevel]

Hahaha

Maybe because if he had converted it to dm, the values would be too small, and the scale would be "Difficult"- that's precisely that seems to be irritating him in the report , that the scale chosen by candidates was too difficult to interpret. Plus, the mark allocation is not really worth the hard work we have to go through just to get to the retarded values; normally, we only convert to dm3 to show to the examiner that "OMG! I am so damn practical! I totally hate cm3." Maybe te examiner's trying to use a short cut. But what we learn from this is that we do not really have to convert cm3 to dm3 when plotting a graph... hopefully i'm not wrong with my assumption cuz now i'm confused that if such a question does come in the exam, will the examiner accept my conversion or will he suddenly decide to become all "no u have to convert to dm3 or ur gettin a ZERO"?
Hasbuna Allah wa Ni'mal Wakeel!

Lol! True! XD I think it's just one of those random papers that unlucky people stumble upon! The examiners have learnt their lessons in making awkward papers, the recent are much more doable Can I ask what would you label the axis?

 

[MaxStudentALevel]

And they are quite lenient in the sense that if a lot of papers have made the mistake it usually does get accounted for. knowitall10

 

[iKhaled]

Maybe because if he had converted it to dm, the values would be too small, and the scale would be "Difficult"- that's precisely that seems to be irritating him in the report , that the scale chosen by candidates was too difficult to interpret. Plus, the mark allocation is not really worth the hard work we have to go through just to get to the retarded values; normally, we only convert to dm3 to show to the examiner that "OMG! I am so damn practical! I totally hate cm3." Maybe te examiner's trying to use a short cut. But what we learn from this is that we do not really have to convert cm3 to dm3 when plotting a graph... hopefully i'm not wrong with my assumption cuz now i'm confused that if such a question does come in the exam, will the examiner accept my conversion or will he suddenly decide to become all "no u have to convert to dm3 or ur gettin a ZERO"?
Hasbuna Allah wa Ni'mal Wakeel!

haha..whoever made this type of question surely wanted to make victims of this exam suffer a lot because this question is worth more than 5 marks even!

but no if we talk in a pure chemistry language then we must convert to dm if we have our concentration in moldm^-3

 

[iKhaled]

And they are quite lenient in the sense that if a lot of papers have made the mistake it usually does get accounted for. knowitall10

i didn't get this :S what do u mean ?

 

[knowitall10]

Hahaha

Lol! True! XD I think it's just one of those random papers that unlucky people stumble upon! The examiners have learnt their lessons in making awkward papers, the recent are much more doable Can I ask what would you label the axis?

I labelled concentration of succinic acid in the water layer on the x-axis and the conc of succinic acid in the ether layer on the y-axis... but i don't know if i'm right cuz i can't really decide which one is independent. Ask iKhaled...

 

[MaxStudentALevel]

i didn't get this :S what do u mean ?

I meant that usually, if a certain problem is faced by a majority of otherwise able candidates they usually make allowances for the question as it clearly isn't a fault of the chemistry knowledge of the student, rather the confusion set in the question. I dont know If they did or didn't for this paper but yeah... I've seen instances of it in P4

 

[MaxStudentALevel]

@

I labelled concentration of succinic acid in the water layer on the x-axis and the conc of succinic acid in the ether layer on the y-axis... but i don't know if i'm right cuz i can't really decide which one is independent. Ask iKhaled...

YES that's right. *facepalm* it's the partition coefficient we're trying to find here DUH! Thanks!

 

[MaxStudentALevel]

I labelled concentration of succinic acid in the water layer on the x-axis and the conc of succinic acid in the ether layer on the y-axis... but i don't know if i'm right cuz i can't really decide which one is independent. Ask iKhaled...

And there is no independent dependent here. Uniquely, either can be on either axis

 

[iKhaled]

I meant that usually, if a certain problem is faced by a majority of otherwise able candidates they usually make allowances for the question as it clearly isn't a fault of the chemistry knowledge of the student, rather the confusion set in the question. I dont know If they did or didn't for this paper but yeah... I've seen instances of it in P4

but will that affect the total mark of the paper? like for example if a question has been canceled because the majority of the candidates didn't do it and its worth 5 marks the total mark of the paper will be 95 for example instead of 100 ?

 

[knowitall10]

And there is no independent dependent here. Uniquely, either can be on either axis

Oh oh, alright... thanks.. then why does the examiner complain about the dependant and independent in the examiner's report? in the second para of part b?

 

[MaxStudentALevel]

but will that affect the total mark of the paper? like for example if a question has been canceled because the majority of the candidates didn't do it and its worth 5 marks the total mark of the paper will be 95 for example instead of 100 ?

I'm pretty sure thats the only way to make allowances. Either that or giving the marks to all candidates. But thats not something to stress about. Point is, be vigilant and read everything closely and make intelligent informed decisions on the paper!
IA We wont have to face anything so weird!

 

[MaxStudentALevel]

Hold on,

Oh oh, alright... thanks.. then why does the examiner complain about the dependant and independent in the examiner's report? in the second para of part b?

Let me go check.... But either should be allowed here, it's an investigation.

 

[MaxStudentALevel]

Oh oh, alright... thanks.. then why does the examiner complain about the dependant and independent in the examiner's report? in the second para of part b?

Just give me a few minuted to attempt the graph then i'll check and compare the ER

 

[knowitall10]

but will that affect the total mark of the paper? like for example if a question has been canceled because the majority of the candidates didn't do it and its worth 5 marks the total mark of the paper will be 95 for example instead of 100 ?

I don't think they'll cancel the paper... they might just be lenient. beacuse its not just us giving this exam: Pakistan, India, Dubai (Mostly Paks and Ind's), Saudi Arabia... and out of all of them, its just the Saudi candidates (regardless of the nationality) who are the dumbest (lol jk). Pak's and Ind's have their IQ levels peaking higher than mount everest... what i'm sure of is that the grade threshold would be lowered. plus, p5 doesnt really play an important role in our overall grades.. its our AS and P4 that carry the greatest weight.

 

[iKhaled]

Just give me a few minuted to attempt the graph then i'll check and compare the ER

show ur graph when u r done pls!!

 

[knowitall10]

show ur graph when u r done pls!!

Yesss!! Please!

 

[knowitall10]

I'm pretty sure thats the only way to make allowances. Either that or giving the marks to all candidates. But thats not something to stress about. Point is, be vigilant and read everything closely and make intelligent informed decisions on the paper!
IA We wont have to face anything so weird!

Hey, MaxStudentALevel, i'm not studying in Pakistan.."intelligent informed decisions" doesnt apply here