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Author Topic: Edexcel CHEMISTRY DOUBTS!!!!  (Read 254117 times)

Offline Malak

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1065 on: May 18, 2011, 08:10:41 pm »
Quote from: NightHawkerr on May 18, 2011, 08:01:34 pm
Hi ya'll. Im doing AS Chem, and i was wondering if you guys could help me out.. What should I be studying for Unit 3 Alt. to Practical? Are there like specific experiments I should concentrate more on? & the syllabus has changed since 2008 right, that means I should only study past papers from 2009 and 2010?
 Thanks, you guys are the best  :D

I suggest that you should check the specification which mentions the experiments you should know and study according to that.
Also memorise some common test, like for gases and organic test in the syllabus, colour changes etc.
And do learn the techniques for titration it always comes up
And some basic calculations like moles and stuff from IG

« Last Edit: May 18, 2011, 08:12:34 pm by ang3l »
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Offline The Golden Girl =D

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1066 on: May 19, 2011, 07:39:23 am »
Guys is there any need for me to revise Chromatography for the Unit 3 exam. *I don't remember it much*
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Offline Uchia

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1067 on: May 19, 2011, 07:51:54 am »
no need to do that

chromotography is for the A2 only not the AS
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Offline ksitna

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1068 on: May 19, 2011, 02:35:59 pm »
can you please tell me where i can find the chemistry specification?
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elemis

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1069 on: May 19, 2011, 02:37:58 pm »
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Offline Uchia

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1070 on: May 19, 2011, 03:01:32 pm »
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Offline ksitna

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1071 on: May 19, 2011, 03:04:44 pm »
thank you guys! :D
so much!
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Offline NidZ- Hero

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1072 on: May 20, 2011, 06:06:17 am »
Hey guys why does only tertiary doesnt react while secondary n primary does wid acidified postassium dichromate
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Offline guMnam

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1073 on: May 20, 2011, 07:25:22 am »
tertiary wat ??
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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1074 on: May 20, 2011, 07:32:27 am »
Quote from: Nidzzz on May 20, 2011, 06:06:17 am
Hey guys why does only tertiary doesnt react while secondary n primary does wid acidified postassium dichromate

you mean tertiary Alcohol ... well it's because the carbon that's bonded to the OH group is bonded to THREE other carbons where as in the secondary alcohol the carbon bonded to the OH group is only bonded to TWO carbons and a HYDROGEN ..... Remember one of the definitions of Oxidation is loss of hydrogen and since the tertiary is NOT bonded to ANY HYDROGENS that is why the tertiary is NEVER going to get oxidized ;)


I hope you got it :)
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Offline Uchia

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1075 on: May 20, 2011, 09:36:02 am »
Kistna ur doing AS or A2
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Offline 7d

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1076 on: May 20, 2011, 01:22:57 pm »
Quote from: Saladin on May 08, 2010, 06:50:59 am
Post 'em all here!!!!

I do Edexcel AS chemistry!




well
im studying chem and i was wondering if anyone cn give me some advice on how to study organic chemistry and unit3
the problem with unit 3 is the detailed questions following the experiments
is there any site where i cn find experiments and their details and unit3 revision in general ?!
i already have the cgp revision guide...


also
in the syllabus it says :

explain why a metal halide and concentrated sulphuric acid should not be used when making a bromoalkane or an iodoalkane


treatment of haloalkanes iwth water containing dissolved silver nitrate ??


demonstrate an understanding of why it is helpful to classify reagents



help/?? i dont understand these topics any help will be appreciated
thank you so much :)


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elemis

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1077 on: May 20, 2011, 01:28:48 pm »
H2SO4 is a very strong oxidising agent, hence, a metal halide (where the halide is Bromine or Iodine) would be oxidised straight to Bromine/Iodine and a mixture of sulphur compounds.

You'd be left with very little Hydrogen Bromide or Hydrogen Iodide which is required to form a bromoalkane or iodoalkane.

Silver Nitrate reacts with a chloroalkane to form a white ppt., a bromoalkane to forma a cream ppt. and  a iodoalkane to form a yellow ppt.

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Offline guMnam

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1078 on: May 20, 2011, 03:45:04 pm »
err...
just a lil confusion... wats the difernce in a free radical and a -ve ion ??
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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1079 on: May 20, 2011, 03:49:34 pm »
Quote from: guMnam on May 20, 2011, 03:45:04 pm
err...
just a lil confusion... wats the difernce in a free radical and a -ve ion ??

free radical is  a specie that has an unpaired electron  where as -ve ion is an atom that has one less electron

I hope I helped :)
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