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Chemistry: Post your doubts here!

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elimination = dehydration my teacher said me once :'| it creates double bond no? :'|
Elimination removes two units while dehydration removes only Hyrdrogen.

comparison b/w sub and eli

image83.gif
 
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Aslm...
What does this part of the chemistry syllabus means? "(h) show understanding of, and use, the Brønsted-Lowry theory of acids and bases, including the use of the acid-I, base-II concept"
What's the acid-1, base 11 concept means?
 
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People .. is this answer , the same as mine ?
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s13_qp_22.pdf
Q5 c(ii)

marking scheme : >CO or carbonyl absent
my answer : It is not ketone .. (ketone absent)

At last .. Is carbonyl the same as ketone ?

I'd write Carbonyl not present OR Aldehyde/Ketone not present.

Just writing ketone not present doesn't say whether if aldehyde is present or not and since it's DNPH if it's negative, there's no way either is present so go with carbonyl.
 
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People .. is this answer , the same as mine ?
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s13_qp_22.pdf
Q5 c(ii)

marking scheme : >CO or carbonyl absent
my answer : It is not ketone .. (ketone absent)

At last .. Is carbonyl the same as ketone ?

No.

part ii is reaction with 2,4 DNPH.. which tells us if there is a carbonyl group present or not.

Carbonyl = Ketone AND Aldehyde both not just ketone..

I mean since you have already told in part i, that it's not a aldehyde the examiner might give you marks for it's not a ketone. But I wouldn't risk it.

The correct Answer for this will be. "The compound doesn't have a carbonyl group" or "No Ketone or Aldehyde present in compound R".
 
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What is meant by heating to a constant mass? This term is often used in Paper 5. The question was that how you would ensure that decomposition is complete and the answer suggested heating to a constant mass. Any idea people? Thank You
 
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no. H2 and Ni only reduces Alkenes to alkanes

btw check this image. I found it in a doc. It summarizes which and what get oxidize and reduce.
View attachment 41128
View attachment 41129
no.. i said that H2 n Ni reduces both alkenes n carbonyl compounds... n u said that they only reduce alkenes...
i didn't know that H2 and Ni reduce CHO but the markscheme of s13/21 says so.
but how is it possible that POTASSIUM PERMANGANATE CAN NOT OXIDISE CHO into CO2H? that is not possible. this oxidising agent is an EXTREMELY powerful reagent. and it will oxidise almost everything. if very concentrated and heated it can oxidise all Carbons and hydrogen in any organic compound into CO2 and H2O. i believe this is another time CIE is wrong. first time being that elimination occurs in alcohol.
 
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i didn't know that H2 and Ni reduce CHO but the markscheme of s13/21 says so.
but how is it possible that POTASSIUM PERMANGANATE CAN NOT OXIDISE CHO into CO2H? that is not possible. this oxidising agent is an EXTREMELY powerful reagent. and it will oxidise almost everything. if very concentrated and heated it can oxidise all Carbons and hydrogen in any organic compound into CO2 and H2O. i believe this is another time CIE is wrong. first time being that elimination occurs in alcohol.
KMnO4 can oxidise CHO in the presence of H2SO4....
 
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Is it okay to draw the displayed formulae instead of the structure formulae in the exam ? or we should stick to structural formula as asked ? and will they reduce marks or what ?!
 
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lol :D n KMnO4 cn only oxidise aldehydes
it must b just to keep everythng simple for our age group... they knw everythng mch better thn us...
i am talking after reading research papers from top universities including university of new york.
and that can NOT be wrong. I have even seen come textbook used in BS in chemistry in cambridge university containing things that are against our A level syllabus.
they know everything but they have simplified the things to the point of being wrong. and i can handle a syllabus 10X the current size. and i hate to learn wrong things.
 
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