Chemistry: Post your doubts here!

[Soldier313]

Aoa wr wb
Can someone please help me with qn 7 c ii of this paper, i managed to do all the calculations, but i can't decide whether this -O-CH3 is substituted on the 4th carbon on the benzene ring
oh and please also look at qn 8b of the same paper, i believe the ms has a mistake?


http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w09_qp_41.pdf
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w09_ms_41.pdf

Thanx a lot

 

[fadilah]

In the chemistry AS syllabus we are supposed to know how chlorine is used in water purification and the environmental significance of halogens and their compounds. Can anybody help me out?

 

[MaxStudentALevel]

Aoa wr wb
Can someone please help me with qn 7 c ii of this paper, i managed to do all the calculations, but i can't decide whether this -O-CH3 is substituted on the 4th carbon on the benzene ring
oh and please also look at qn 8b of the same paper, i believe the ms has a mistake?


http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w09_qp_41.pdf
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w09_ms_41.pdf

Thanx a lot

Basically, they'll allow it anywhere because I don't think it's incur syllabus to know why it'd be on the 4th carbon.
I, however came Accross it in my Internet search studies lol:
-with phenol, PARA (on the 4th carbon) substitution always occurs.
-IF para is blocked by another compound, the ORTHO occurs, which is C#2

 

[MaxStudentALevel]

@fap

In the chemistry AS syllabus we are supposed to know how chlorine is used in water purification and the environmental significance of halogens and their compounds. Can anybody help me out?

I suggest you do a quick google search and refresh your knowledge bank.
I'd do it for you, but I'm actually pretty busy!

 

[knowitall10]

can u fill the table and draw the graph because i am stuck with this question too. i tried to do it yesterday and i spent hours on it but its so difficult to draw the graph

Oh alright....
Succinate acid is being dissolved in the water and ether:
The 10 cm3 water layer contains succinate
the 25 cm3 ether layer also contains succinate.
(we take these two as the volume of succinate that is being reacted with NaOH)
To calculate the con of succinate in water layer: Moles of NaOH=Moles of Succinate
Moles of NaOH= B/1000 x 0.1 = 0.1B/1000
Moles of Succiante= 10/1000 x D = 10D/1000
to find column D: (0.1B/1000) / (10/1000) =0.01B
The same method applies to find the concentration of succinate in ether layer

Plot the graph, and you get the line of best fit passing through the origin
Hope i helped you guys!

 

[iKhaled]

Oh alright....
Succinate acid is being dissolved in the water and ether:
The 10 cm3 water layer contains succinate
the 25 cm3 ether layer also contains succinate.
(we take these two as the volume of succinate that is being reacted with NaOH)
To calculate the con of succinate in water layer: Moles of NaOH=Moles of Succinate
Moles of NaOH= B/1000 x 0.1 = 0.1B/1000
Moles of Succiante= 10/1000 x D = 10D/1000
to find column D: (0.1B/1000) / (10/1000) =0.01B
The same method applies to find the concentration of succinate in ether layer

Plot the graph, and you get the line of best fit passing through the origin
Hope i helped you guys!

To calculate the con of succinate in water layer: Moles of NaOH=Moles of Succinate this is wrong. because 2 moles of NaOH reacts with 1 mole of the acid because the acid has 2 carboxylic groups not one. its so hard to find a scale for that graph..

 

[knowitall10]

Allak ka maseeha ho yar aap i seriously didnt know anything , thankyou you mademit crystal clear for me Alhumdulillah . ALLAH hum sab ko maamyab karen , Ameen . Well i am so worried for papaer 4 i dont have time to revise AS syllabus at all, and they give a lot of it :O

Don't worry, it'll happen. Keep faith in Allah and pray a lot, there're still 10 days 15 days to p4, revise only the group chemistry and the organic of AS, not the whole syll really. InshAllah, we'll pass

 

[knowitall10]

To calculate the con of succinate in water layer: Moles of NaOH=Moles of Succinate this is wrong. because 2 moles of NaOH reacts with 1 mole of the acid because the acid has 2 carboxylic groups not one. its so hard to find a scale for that graph..

Yeah, you have a point... hmm.. alright then, try the method i told you with 2moles instead of 1.. I'll try as well; if i get the scale, i'll let you know inshAllah.
Thanks a lot for telling me though
Jazak Allahu Khair

 

[iKhaled]

Yeah, you have a point... hmm.. alright then, try the method i told you with 2moles instead of 1.. I'll try as well; if i get the scale, i'll let you know inshAllah.
Thanks a lot for telling me though
Jazak Allahu Khair

thank you so much if you are able to get a perfect scale and a good graph please do upload a picture of it, if it is ok

 

[knowitall10]

To calculate the con of succinate in water layer: Moles of NaOH=Moles of Succinate this is wrong. because 2 moles of NaOH reacts with 1 mole of the acid because the acid has 2 carboxylic groups not one. its so hard to find a scale for that graph..

Btw, read the whole mark scheme, i dont think the number of moles really matters cuz we'll just get smalller values. the marking scheme just wants the line passing through the origin, and its not really stating the method of finding the concentration. later on in the paper, we have to find the gradient of our line: My gradient according to the method i told u is 0.062- what i dont understand abou the marking scheme is that it says, "...must be in the order of 16.3/0.062". and further on: "yes, since the results produce a good linear/straight line graph, the procedure is OK".
so.. what do you think? Did you try your method?

 

[iKhaled]

Btw, read the whole mark scheme, i dont think the number of moles really matters cuz we'll just get smalller values. the marking scheme just wants the line passing through the origin, and its not really stating the method of finding the concentration. later on in the paper, we have to find the gradient of our line: My gradient according to the method i told u is 0.062- what i dont understand abou the marking scheme is that it says, "...must be in the order of 16.3/0.062". and further on: "yes, since the results produce a good linear/straight line graph, the procedure is OK".
so.. what do you think? Did you try your method?

did u read the examiner report of this question ?

 

[knowitall10]

thank you so much if you are able to get a perfect scale and a good graph please do upload a picture of it, if it is ok

OH NO!!! I think it does matter! Read the examiner's report on this question. column D's heading must be 0.1B/20 based on the 2:1 mole ratio principle!
http://papers.xtremepapers.com/CIE/...and AS Level/Chemistry (9701)/9701_w10_er.pdf

 

[knowitall10]

I

did u read the examiner report of this question ?

just did

 

[sameer_ijaz]

do v get e.c.f for mole calculation ?

 

[knowitall10]

do v get e.c.f for mole calculation ?

we should....

 

[knowitall10]

did u read the examiner report of this question ?

The examiner's report also tells what scale we can use ... u put me in a hassle
The answer's right there!
Anyway, Jazak Allah, atleast you made me attempt this weirdo paper!
May Allah make your exam easy for you and remove any obstacles from your path to success! Aameen!

 

[iKhaled]

The examiner's report also tells what scale we can use ... u put me in a hassle
The answer's right there!
Anyway, Jazak Allah, atleast you made me attempt this weirdo paper!
May Allah make your exam easy for you and remove any obstacles from your path to success! Aameen!

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? :/

 

[MaxStudentALevel]

The examiner's report also tells what scale we can use ... u put me in a hassle
The answer's right there!
Anyway, Jazak Allah, atleast you made me attempt this weirdo paper!
May Allah make your exam easy for you and remove any obstacles from your path to success! Aameen!

The examiner's report also tells what scale we can use ... u put me in a hassle
The answer's right there!
Anyway, Jazak Allah, atleast you made me attempt this weirdo paper!
May Allah make your exam easy for you and remove any obstacles from your path to success! Aameen!

What paper were you guys discussing ?

 

[MaxStudentALevel]

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? :/

^^^

 

[iKhaled]

What paper were you guys discussing ?

oct/nov 2010 paper 53