Author Topic: Chemistry Help HERE ONLY !!  (Read 106129 times)

Offline THEIGBOY

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Re: Chemistry Help HERE ONLY !!
« Reply #615 on: May 31, 2009, 10:49:38 am »
GodFather93, THEIGBOY are on
www.drop.io/theigboy
for a group chat on anything related to IGCSE CHEMISTRY
just scroll down and open the chat menu
(chnge ur nick to correspond with studenforums)

By the way it was GodFather93's idea
Come ASAP and ask any question and we'll try our best to answer

Offline thukon

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Re: Chemistry Help HERE ONLY !!
« Reply #616 on: May 31, 2009, 12:02:13 pm »
Someone said most alkalis are soluble. WRONG!! All alkalis are soluble, but not all bases are soluble. Soluble bases are called alkalis.

Offline emi

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Re: Chemistry Help HERE ONLY !!
« Reply #617 on: May 31, 2009, 12:05:35 pm »
shogun and sweetsh ,, did u want a list of insoluble salts ??
well if you did then here is it

-all carbonates except those of group 1 metals and ammonium carbonate
-all hydroxides except those of group 1 metals and those of calcium, strontium and barium
-barium, calcium and lead sulphates
-the chlorides, bromides and iodides of both silver and lead

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Offline evilzurg307

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Re: Chemistry Help HERE ONLY !!
« Reply #618 on: May 31, 2009, 12:07:24 pm »
Cation reactivity series:
Please-K
sent-Na
cats-Ca
monkeys-Mg
and-Al
zebras-Zn
in-Fe
large-Pb
hired-H
cages.-Cu
Make-Hg
sure-Ag
padlocked.-Pt



Thanks that helped a lot!
+rep

Offline emi

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Re: Chemistry Help HERE ONLY !!
« Reply #619 on: May 31, 2009, 12:11:25 pm »
can some one give me mark scheme for November 2003 paper3 ?  the one on Free exam paper is totally unrelated

ricko the one u posted was for 2005 i want 2003
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Offline SGVaibhav

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Re: Chemistry Help HERE ONLY !!
« Reply #620 on: May 31, 2009, 12:17:13 pm »
Give
examples
of Oxidising agent and Reducing Agnet

Test for Oxidising agent

Offline ig_kid

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Re: Chemistry Help HERE ONLY !!
« Reply #621 on: May 31, 2009, 12:22:41 pm »

nid404

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Re: Chemistry Help HERE ONLY !!
« Reply #622 on: May 31, 2009, 12:24:45 pm »
can some one give me mark scheme for November 2003 paper3 ?  the one on Free exam paper is totally unrelated

ricko the one u posted was for 2005 i want 2003

here

Offline archangel

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Re: Chemistry Help HERE ONLY !!
« Reply #623 on: May 31, 2009, 12:29:38 pm »
@shogun

heres the list: (just the ones we need for igcse only)

                   Soluble:                                           Insoluble:
                 All nitrates

               Most Chlorides                   Except for Silver Chloride (AgCl) and Lead (II) Chloride (PbCl2)[but can be dissolved in hot water]

              Most Sulphates                   Except for Calcium Sulphate (CaSO4), Barium Sulphate (BaSO4) and Lead (II) Sulphate (PbSO4)

      Potassium Carbonate (K2CO3)                  Most Carbonates
       Sodium Carbonate (NaCO3)
    Ammonium Carbonate (NH4)2CO3

Offline ig_kid

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Re: Chemistry Help HERE ONLY !!
« Reply #624 on: May 31, 2009, 12:34:04 pm »
Oxidising agents:
Cl2
Fe3+
Potassium iodate
potassium bromate
H2O2

Reducing agents:
Hydrogen Sulphide
Fe2+
SO2

nid404

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Re: Chemistry Help HERE ONLY !!
« Reply #625 on: May 31, 2009, 12:36:12 pm »
Give
examples
of Oxidising agent and Reducing Agnet

Test for Oxidising agent

potassium dichromate is an oxidisng agent
Carbon, Carbon monoxide r reducing agents

but there r so many more depending on different redox reactions

testing....as in color change with change in oxidation state???
if so then ive ans it before.....u need to know manganate to manganese salt(reduction, color change from purple to colorless) and iodide to iodine(oxidation, colorless to brown)




Offline emi

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Re: Chemistry Help HERE ONLY !!
« Reply #626 on: May 31, 2009, 12:36:37 pm »
the thing is that if u see that markscheme and match it with the Question paper if doesnt match at all .. in Question paper the first Questions talk about liquid fuels obtained from petroleum while in the mark scheme it says 1) different boiling points ??

part b) says magnesium carbonate reactions with HCL to form a salt name that salt  
the markscheme says Volume decreases for forward reaction.


what i mean is that its not related at all  
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Offline Kim

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Re: Chemistry Help HERE ONLY !!
« Reply #627 on: May 31, 2009, 12:50:35 pm »
test for oxidising agents
potassium iodide changes from colourless to yellow brown when added to a oxidising agent

test for reducing agent
add potassium dichromate colour colour changes from orange to green
add potassium manganate colour changes from purple to colourless
After all is said and done, more is said than done.

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The early bird may get the worm, but the second mouse gets the cheese.

nid404

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Re: Chemistry Help HERE ONLY !!
« Reply #628 on: May 31, 2009, 12:51:08 pm »
the thing is that if u see that markscheme and match it with the Question paper if doesnt match at all .. in Question paper the first Questions talk about liquid fuels obtained from petroleum while in the mark scheme it says 1) different boiling points ??

part b) says magnesium carbonate reactions with HCL to form a salt name that salt  
the markscheme says Volume decreases for forward reaction.


what i mean is that its not related at all  

i  think ur looking at 2 diff papers cuz it's perfectly matching for me.

nid404

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Re: Chemistry Help HERE ONLY !!
« Reply #629 on: May 31, 2009, 12:55:37 pm »
ill put the question paper up for u emi