Edexcel AS Chemistry Unit 2 Thread Watch

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Phalange
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#221
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#221
(Original post by SK-mar)
ok for the phosphoric acid one: might they ask, how would you know that the reaction has taken place, or what would you observe when the reaction is taking place would you just say steamy fumes produced from the hydrogen halide? or is there anything else?
Not that I know of, no... Only steamy fumes from hydrogen halides that turn damp blue litmus red..
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bluefire
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#222
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(Original post by SK-mar)
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chlorobromodifluoromethane (remember its best to put it in alphabetical order and it is simply a one carbon molecule so is a methane compound.

Methyl orange:
red in acid
orange at neutral (hence the name methyl orange)
yellow in alkali

phenolphthalein:
colourless in acid
pink in alkali
if you are titrating an alkali with acid they want you to put pink > colourless as the colour change.

starch for iodine titrations:
blue-black to colourless for end of titration

hope this helps
hey SK-mar i have a question answer quick plz thanks.

cl2 is contaminated with either br- or i- .
name a solvent and observation for it ? its in jan 2010 i guess q17/q18
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obviouslystudying
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#223
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Particular Expectations: PCl4 ion
Catalyst, definition or something related anyway.

Lets see!
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pervy_sage
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#224
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#224
(Original post by SK-mar)
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chlorobromodifluoromethane (remember its best to put it in alphabetical order and it is simply a one carbon molecule so is a methane compound.

Methyl orange:
red in acid
orange at neutral (hence the name methyl orange)
yellow in alkali

phenolphthalein:
colourless in acid
pink in alkali
if you are titrating an alkali with acid they want you to put pink > colourless as the colour change.

starch for iodine titrations:
blue-black to colourless for end of titration

hope this helps



you sir are a legend

I just wanted to know the basic info in how to know which compound will absorb Ir radiation?
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obviouslystudying
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#225
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(Original post by bluefire)
hey SK-mar i have a question answer quick plz thanks.

cl2 is contaminated with either br- or i- .
name a solvent and observation for it ? its in jan 2010 i guess q17/q18
Why not test for Halide ions? Iodine would give off more products, like the H2S rotten egg smelling gas.
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obviouslystudying
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(Original post by pervy_sage)
I just wanted to know the basic info in how to know which compound will absorb Ir radiation?
Depends on the functional group. Different functional groups absorb IR @ different wavelengths. Use the formula booklet for reference, bu quote from the given graph NOT from the booklet when explaining.
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Soda__Dreamer
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#227
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#227
Who is bricking tomorrow?!
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hilly22
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#228
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#228
me
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SK-mar
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#229
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(Original post by pervy_sage)
you sir are a legend

I just wanted to know the basic info in how to know which compound will absorb Ir radiation?
Basically it has to be a compound which is polar because when it absorbs IR radiation it vibrates and due to its polarity will stretch and bend. However, one easy way i remember whether it will absorb is simply by recognising the bond:
C-O
C=O
C-H
O-H

these are some of the most common bond types that absorb and normally one trick question is whether C-H will absorb because many people think its not polar but in actual fact it has the slightest polarity which will absorb IR radiation.
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dunnoaboutme
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#230
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#230
im nervous god dam homiez
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SK-mar
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#231
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(Original post by bluefire)
hey SK-mar i have a question answer quick plz thanks.

cl2 is contaminated with either br- or i- .
name a solvent and observation for it ? its in jan 2010 i guess q17/q18
ermm if your thinking the same thing i am then a solvent would be a hydrocarbon solvent such as volasil.
chlorine = pale green/colourless
bromine = orange
iodine = pink/violet
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SK-mar
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(Original post by dunnoaboutme)
im nervous god dam homiez
haha same....GOOD LUCK EVERYONE!
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areyousure?
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#233
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#233
I am off to bed.

Good Luck everyone!! =D
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stressedatschool
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#234
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#234
Hey everyone,
I haven't seen a forum for this so just wondered what everyone thought of the paper.
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EierVonSatan
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#235
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#235
http://www.thestudentroom.co.uk/anno...hp?f=130&a=482
Craydot
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#236
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#236
How did everyone find it?
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lpmad
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#237
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#237
It was good i guess, multiple choice was much harder compared to unit 1 lol
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TomSouthwell
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#238
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#238
There was a question on, a Fullerene molecule C60 , and was it that the melting temperature was higher?
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lpmad
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#239
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#239
no it was that they had free electrons
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Craydot
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#240
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#240
Yeah, definitely!...the concerntration/mol questions weren't very straight forward
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