Chemistry: Post your doubts here!

[raamish]

in ms its saying clock started late

 

[pearl angel]

Yeah, i was just going to tell you guys that i'm a student just like you... so these are my explanations based on what i understand really. i strongly suggest you verify my explanation with a teacher or something.. I'm just trying to help here I might be wrong too... and to answer Raamish, i would only look at the distance of the point from the line a drew, not the x or y axis. and to answer pearlangel, if there're three points then i would look at whther the third point is closer to the one above or below the line, and based on that, i would place my answer. but i do not know if this is the right way to look at it.
Hopefully i helped you a little if not much

i think u helped alot because your explanation about the 3 points makes sense so thanks alot

 

[knowitall10]

in ms its saying clock started late

the ms doesnt say anything about the clock.. ur talking about june 2012 v51 right?

 

[knowitall10]

i think u helped alot because your explanation about the 3 points makes sense so thanks alot

No problem

 

[raamish]

sorry i was askin abt n11 51 point 7 is away frm line so should we take it on y axis. in point 7 the log(rate of rxn) is more negative so rate of rxn less and time greater so clock started late. Is this the correct reasoning for the anomalous point?

 

[PhyZac]

knowitall10

I am really sorry for disturbing, but i have some problem in Oct/Nov 2009 v1. Question 1 (e)
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w09_qp_51.pdf
The mark scheme said that it define the extent of the experiment.

My question is what do they mean by that here?

 

[knowitall10]

sorry i was askin abt n11 51 point 7 is away frm line so should we take it on y axis. in point 7 the log(rate of rxn) is more negative so rate of rxn less and time greater so clock started late. Is this the correct reasoning for the anomalous point?

Can you upload your graph please? I think my anomalous are different..

 

[raamish]

my point 7 at 3.19 time is below the line and point 4 is above the line at 3 time. is yours diff

 

[knowitall10]

knowitall10

I am really sorry for disturbing, but i have some problem in Oct/Nov 2009 v1. Question 1 (e)
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w09_qp_51.pdf
The mark scheme said that it define the extent of the experiment.

My question is what do they mean by that here?

No no its alright I'm happy to help you.
Umm, i think "defines the extent of the reaction" means that because the burette is very very accurate, it basically assures the volume at which the end point of the reaction is reached. i think this is what "finishing line" would mean. i didnt really read the whole question, i'm explaining the mark scheme, so please tell me if i'm going off topic here..
in other words, the burette gives us a very accurate value so by "to enable comparison", the ms might mean that the volume of thiosulfate is less likely to change so there's fair comparison.

 

[knowitall10]

my point 7 at 3.19 time is below the line and point 4 is above the line at 3 time. is yours diff

Raamish, did you plot log(rate of reaction) against 1/T or log(rate of reaction) against time?

 

[PhyZac]

No no its alright I'm happy to help you.
Umm, i think "defines the extent of the reaction" means that because the burette is very very accurate, it basically assures the volume at which the end point of the reaction is reached. i think this is what "finishing line" would mean. i didnt really read the whole question, i'm explaining the mark scheme, so please tell me if i'm going off topic here..
in other words, the burette gives us a very accurate value so by "to enable comparison", the ms might mean that the volume of thiosulfate is less likely to change so there's fair comparison.

Thank you so much Jazaki Allah khiaran.

Yes i got it, and u rnt going off topic here, infact u explained really well. Ma Sha Allah.

I dont know whether u will check this paper or not in case u do, do inform me how does ensures end of reaction, i cudnt understand the equation but was lucky to solve the questions in a manner they wanted.

 

[knowitall10]

Thank you so much Jazaki Allah khiaran.

Yes i got it, and u rnt going off topic here, infact u explained really well. Ma Sha Allah.

I dont know whether u will check this paper or not in case u do, do inform me how does ensures end of reaction, i cudnt understand the equation but was lucky to solve the questions in a manner they wanted.

Wa iyyak(i)
(idk if ur male or female)
sure thing, i'll look at it now in fact I'll let you know soon inshAllah.

 

[knowitall10]

Thank you so much Jazaki Allah khiaran.

Yes i got it, and u rnt going off topic here, infact u explained really well. Ma Sha Allah.

I dont know whether u will check this paper or not in case u do, do inform me how does ensures end of reaction, i cudnt understand the equation but was lucky to solve the questions in a manner they wanted.

because we're carrying out different experiments, we have to keep everything constant except the concentration of potassium persulfate if i'm not wrong. So a fair comparison would only happen if the volume of sodium thiosulfate remains constant (the sodium thiosulfate determines the number of iodide ions which must also remain constant throughout the experiments- so this is an important step because a slight change in the volume of thiosulfate would affect the iodide ion conc.) so we use a burette because we can accurately keep the volume of thiosulfate constant for each experiment. Am i clear.. or did i just mess it up for you?

 

[raamish]

lg against against 1/T. hey its getting late brother. What is the timezone u live in. i want to ask the anomalous questions from u tomorrow and then maybe i will have a better understanding inshallah

 

[PhyZac]

because we're carrying out different experiments, we have to keep everything constant except the concentration of potassium persulfate if i'm not wrong. So a fair comparison would only happen if the volume of sodium thiosulfate remains constant (the sodium thiosulfate determines the number of iodide ions which must also remain constant throughout the experiments- so this is an important step because a slight change in the volume of thiosulfate would affect the iodide ion conc.) so we use a burette because we can accurately keep the volume of thiosulfate constant for each experiment. Am i clear.. or did i just mess it up for you?

Jazaki Allah khairan...thanks aloooooooooooooooooooooot.

May Allah S.W.T make your exam easy, and have mercy on you Ammeeen.

Well i got it very well. Thank u again

 

[knowitall10]

Jazaki Allah khairan...thanks aloooooooooooooooooooooot.

May Allah S.W.T make your exam easy, and have mercy on you Ammeeen.

Well i got it very well. Thank u again

Wa iyyak(i)!
Aameen!! you're most welcome my friend

 

[knowitall10]

Wa iyyak(i)!
Aameen!! you're most welcome my friend

Oh and don't bother looking for it, here:

 

[6Astarstudent]

1. CH2=CHCH2OH + KMNO4 dilute cold = HOCH2CH(OH)CH2OH? or does the original OH group get oxidised
2. HOOCCOOH + Kmno4 hot = CH3COOH?
3. HCOOH + Kmno4 hot = co2 and h2o so no organic products?

 

[raamish]

i just found a qs from n08 2a) in the table column of Q we have written 0 as 0.00 so shouldnt we write 720.00, but its written 720

 

[knowitall10]

1. CH2=CHCH2OH + KMNO4 dilute cold = HOCH2CH(OH)CH2OH? or does the original OH group get oxidised
2. HOOCCOOH + Kmno4 hot = CH3COOH?
3. HCOOH + Kmno4 hot = co2 and h2o so no organic products?

Look at this diagram for the hot KMnO4 sol. But i don't know about your first question... it should give a di-ol but i don't know if the original OH gp would be oxidised. Wait, i don't think it'll get oxixdised cuz its cold KMnO4 solution..don't you think?