Chemistry: Post your doubts here!

[Xtremite]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s09_qp_4.pdf
in this number-6 part (C) cant we mention phenol and that it will give coloured solution with phenyl amine because it will form coupling?? isnt it?
please help

nooooo. Adding bromine water is the most common and repeated test for phenyls in the past papers. So the test should be the same for phenyl amines too.
I dont think coupling is a test for anything. we just need to know it for reactions etc.

 

[1357913579]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s09_qp_4.pdf
in this number-6 part (C) cant we mention phenol and that it will give coloured solution with phenyl amine because it will form coupling?? isnt it?
please help

after adding nano2+hcl then phenol isnt it??
becuase see in this paper
http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_w08_qp_4.pdf
6(b)
answer is with phenol and same reaction isnt it please someone help as soon as possible

 

[knowitall10]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s09_qp_4.pdf
in this number-6 part (C) cant we mention phenol and that it will give coloured solution with phenyl amine because it will form coupling?? isnt it?
please help

Yeah, but what would your observations be? Why not use aqBromine? What does the marking scheme say?

 

[1357913579]

nooooo. Adding bromine water is the most common and repeated test for phenyls in the past papers. So the test should be the same for phenyl amines too.
I dont think coupling is a test for anything. we just need to know it for reactions etc.

can u please check my above post and reply please
and thanks for hwlping

 

[knowitall10]

exactly. Yes, I will. And you keep me in yours!!

InshAllah

 

[1357913579]

i asked it becuase its not written in maring shceme phenol this time and it was written in the previos year marking sheme now what to do?

 

[knowitall10]

idk how i slept like a dead man :$ anyway can u quote what he said to check it plsss

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w11_qp_43.pdf
Q 3 e (iv)
Yalla....show us

 

[Xtremite]

after adding nano2+hcl then phenol isnt it??
becuase see in this paper
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w08_qp_4.pdf
6(b)
answer is with phenol and same reaction isnt it please someone help as soon as possible

I'm afraid, the mark scheme has mentioned the same test here too.

L not being a phenol doesn't give any observation whereas M being a phenol decolourises bromine water and gives white ppt.

 

[knowitall10]

after adding nano2+hcl then phenol isnt it??
becuase see in this paper
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w08_qp_4.pdf
6(b)
answer is with phenol and same reaction isnt it please someone help as soon as possible

Yeah, that's an alternative answer..but it doesnt say reject aq Bromine now does it?

 

[knowitall10]

I'm afraid, the mark scheme has mentioned the same test here too.

The marking scheme never said anything abt aq bromine. that means its ok. the iodoform test is an alternative.

 

[Xtremite]

The marking scheme never said anything abt aq bromine. that means its ok. the iodoform test is an alternative.

Oh come on. check again. The first phrase for 6(b) is Aqueous Bromine.

 

[1357913579]

I'm afraid, the mark scheme has mentioned the same test here too.

L not being a phenol doesn't give any observation whereas M being a phenol decolourises bromine water and gives white ppt.

ian not saying that br2 is wrong what iam asking is that is diazotizationn coupling correct or not?

 

[Xtremite]

ian not saying that br2 is wrong what iam asking is that is diazotizationn coupling correct or not?

Of course it's correct now that the mark scheme has mentioned it. But why bother? When you can perform a simple test which you have learnt in O level, why go into these complicated tests!

 

[1357913579]

Of course it's correct now that the mark scheme has mentioned it. But why bother? When you can perform a simple test which you have learnt in O level, why go into these complicated tests.

ok thanks alot for your cooperation

 

[Xtremite]

ok thanks alot for your cooperation

Never mention it, long-number.

 

[knowitall10]

Never mention it, long-number.

LOL!!
Sorry dude...got blind for fraction of a sec I ddnt c it
but thanks a lot! Jazaki Allahu Khair

 

[iKhaled]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_qp_43.pdf
Q 3 e (iv)
Yalla....show us

Silent Hunter

alright here is the solution...

first of all we write the equation to check the molar ratio and its CH3COOH + NaOH ---> CH3COONA + H20

now lets calculate the number of moles of the acid and base before the reaction
n of ethanoic acid = 0.25x(10/1000) = 0.0025 mol
n of NaOH = 0.1x(10/1000) = 0.001 mol

now when we mixed them together the total volume of the solution will be 20cm^3 so u can see that ethanoic acid is in excess and the ratio of acid:base:salt is all 1:1:1 so 0.001 mol of salt will be produced and that has a concentration of 0.001/0.02 = 0.05mol/dm^3 and the acid left unreacted in the solution will be 0.0025-0.001 = 0.0015 mol so the concentration of the acid will be 0.0015/0.02 = 0.075

use the equation PH = 4.76 + log(0.05/0.075)
PH = 4.58

thats it..hope u got it!!

 

[biba]

doing the application chapters from the application booklet and chemistry coursebook (roger norris) is enough ryt ?

 

[iKhaled]

doing the application chapters from the application booklet and chemistry coursebook (roger norris) is enough ryt ?

i heard loads of negative feedback about the application booklet..so u better not waste ur time on it !

 

[biba]

i heard loads of negative feedback about the application booklet..so u better not waste ur time on it !

[^__^].. yeah i know, our chem sir did correct some mistakes in it... wel i have learned the concepts, so now i think it would be wise to do the pastpapers?.. cuz i did my core with the pastpapers em just left with the applications :/