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Author Topic: Help in AS Chemistry!  (Read 3206 times)

nid404

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Re: Help in AS Chemistry!
« Reply #15 on: May 30, 2010, 07:57:39 am »
Quote from: The SMA on May 29, 2010, 07:48:23 am
guys i need help on answering On
2) O/N 2008 p2, Q2 (ii),

2c)ii)
 
C+ O2--->CO2     -395kj/mol
H2+ 1/2 O2--->H2O   -286kj/mol

CH2=C=O + 2O2---> 2CO2+ H2O    -1028kj/mol

the reaction's whose enthalpy we want is a combination of the reactions above...figure using hess' law
2C+ H2+ 1/2 O2---> C2H2O 

\delta H = 2X-395+ (-286) - (-1028)
=-48kj/mol
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Offline TJ-56

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Re: Help in AS Chemistry!
« Reply #16 on: May 30, 2010, 08:44:08 am »


   H  H
   |  |
R-C-C -CH2OCOCH3
   |
  CH3

[/quote]

hey, i had the same question but where did the c=c go , is it still there and isnt there supposed to be another hydrogen atom on the 2nd carbon from the left?
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nid404

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Re: Help in AS Chemistry!
« Reply #17 on: May 30, 2010, 08:52:21 am »
i modified my post.

HBr adds across the double bond. It's an addition reaction
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Offline TJ-56

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Re: Help in AS Chemistry!
« Reply #18 on: May 30, 2010, 09:01:46 am »
Quote from: nid404 on May 30, 2010, 08:52:21 am
i modified my post.

HBr adds across the double bond. It's an addition reaction

ok sorry didnt notice that.. thanx for the help anyways!
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Offline TJ-56

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Re: Help in AS Chemistry!
« Reply #19 on: May 30, 2010, 09:08:42 am »
can anyone help me with the bond angle predicting questions? i cant find a pattern whatsoever in bond angle predictions, and my cie book just states a couple of angles but doesnt explain them clearly.. thanks for any help in advance .. i rly appreciate it
 
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Offline girl_92

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Re: Help in AS Chemistry!
« Reply #20 on: May 30, 2010, 11:54:32 am »
there is a que in the past papers of organic  hex-3-enol is oxidised usind hot KMnO4 what will the products be plz reply 
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some people sleep to dream while othrs wakeup to follow dem im the second type how abt u

Offline Meticulous

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Re: Help in AS Chemistry!
« Reply #21 on: May 30, 2010, 12:02:14 pm »
No product. Tertiary alcohols do not oxidize.
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Offline girl_92

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Re: Help in AS Chemistry!
« Reply #22 on: May 30, 2010, 12:42:24 pm »
no its a primary alcoho the structure is

CH3CH2CH=CHCH2CH2OH
ND THE ANSWER IS CH3CH2COOH AND HOOCCH2COOH
 HOW DO YU GET THIS
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some people sleep to dream while othrs wakeup to follow dem im the second type how abt u

Offline girl_92

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Re: Help in AS Chemistry!
« Reply #23 on: May 30, 2010, 12:43:54 pm »
ITS OK I GOT THE ANSWER JUST NOW
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some people sleep to dream while othrs wakeup to follow dem im the second type how abt u

Offline highly_ambitious

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Re: Help in AS Chemistry!
« Reply #24 on: May 30, 2010, 12:52:36 pm »
guyz, i've revised most of the topics for paper 2 chem. i've already done past papers all earlier. now after revision i don't know what should i do?

shall i do all the past papers again or revise ?? plz help!!
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Offline ruby92

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Re: Help in AS Chemistry!
« Reply #25 on: May 30, 2010, 02:49:42 pm »
m/j 2009 variant 1
4 b iii  ??? ???
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Offline moon

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Re: Help in AS Chemistry!
« Reply #26 on: May 30, 2010, 04:43:30 pm »
Can somebody help me in solving question no. 4(c) in June 2001 ppr 2?? Thanks in advance.
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Offline TJ-56

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Re: Help in AS Chemistry!
« Reply #27 on: May 30, 2010, 05:07:15 pm »
please can someone confirm if its an error made in the mark scheme about mj 06 q4 (f) (ii)
where did the carbon atom in the middle go??
Thanks for any help
« Last Edit: May 30, 2010, 05:12:54 pm by TJ-56 »
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Offline sweetie

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Re: Help in AS Chemistry!
« Reply #28 on: May 30, 2010, 07:04:59 pm »
Quote from: TJ-56 on May 30, 2010, 05:07:15 pm
please can someone confirm if its an error made in the mark scheme about mj 06 q4 (f) (ii)
where did the carbon atom in the middle go??
Thanks for any help

i have da same Q., plzzzzzzzzzzzzz  sum1 help
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Offline yinyang

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Re: Help in AS Chemistry!
« Reply #29 on: May 31, 2010, 08:13:19 am »
Quote from: TJ-56 on May 30, 2010, 05:07:15 pm
please can someone confirm if its an error made in the mark scheme about mj 06 q4 (f) (ii)
where did the carbon atom in the middle go??
Thanks for any help

the formula of the allyl alcohol is CH2=CHCH2OH

when this allyl alcohol is heated under reflux with acidified MnO4-  the double bond breaks

so you will have   CH2O   and     COHCH2OH

since it is heated under reflux the products are further oxidised

CH2O  ------->    2CO2  + 2H2O




COHCH2OH  -------->       HO2CCO2H


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