Edexcel A2 Chemistry 6ch04/05 JUNE 2015 Watch

thymolphthalein
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#981
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#981
(Original post by Ripper Phoenix)
thanks so much i've repped you recently so TSR dont let me rep you!! Anyway i'm done with this revision! good luck man!
You too.

Ahah it's alright, not here for the reps. :cool:

I'm off to sleep as well.
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madmenace
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#982
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Hey what tips would u guys give for me on the titration questions like the Ag one in the 2012 paper?

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bbyturtlexox
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#983
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(Original post by madmenace)
Hey what tips would u guys give for me on the titration questions like the Ag one in the 2012 paper?

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read the question
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daisychain_
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#984
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(Original post by ArielHaeems)
4.4 g)ii talks about ethanoic acid and ammonium carbonate. in this reaction,entropy change of the system is positive, since carbon dioxide gas (which is more disordered than the aqueous reactants) is produced. Additionally, the number of product molecules is greater than the number of reactant molecules, further increasing disorder.4.4 g)iii talks about exothermic reactions and the production of a solid, e.g.2Mg + O2 --> 2MgOA solid (MgO) is being formed from a gas (O2), so the entropy change of the system is negative, as the molecules are becoming more ordered. Additionally, two molecules have been produced from three, further decreasing disorder.For exothermic reactions, entropy change of the system is always likely to be negative, since these are reactions which release heat (therefore the system itself cools, and so disorder decreases).
thank you! So is the total entropy change of the last reaction you talked about positive or negative?
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cerlohee
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#985
I'm so nervous for today!! Thanks to everyone who's helping out on this thread and best of luck to you all!!!
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alwaysalex
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Does anyone know if we can do graphs in pencil?
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Wahid1
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#987
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(Original post by alwaysalex)
Does anyone know if we can do graphs in pencil?
Yea just press hard enough


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Wahid1
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#988
Can someone please explain why when the same Kc equation has every concentration halved then Kc= (Kc)^1/2???

I thought only temp affects Kc position


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Ripper Phoenix
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(Original post by alwaysalex)
Does anyone know if we can do graphs in pencil?
(Original post by Wahid1)
Yea just press hard enough


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lol yes use pencil and dont press too hard enough! you don't want your line to look like a thick rope! Draw them normally because they will be scanned anyway
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Ripper Phoenix
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(Original post by Wahid1)
Can someone please explain why when the same Kc equation has every concentration halved then Kc= (Kc)^1/2???

I thought only temp affects Kc position


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I always put values into the equations! helps to understand the kc(i)=kc thing concept. Its just one of those things you have to know
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Ripper Phoenix
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#991
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#991
why isn't the entropy of system always positive for dissolving?
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Nurullahakash
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#992
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#992
Will there be an unofficial markscheme for chemistry too?
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Wahid1
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#993
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#993
Kc help needed pls


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thymolphthalein
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I'm getting 13.3, but the mark scheme says it should be 13.6
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Maham88
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(Original post by thymolphthalein)
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I'm getting 13.3, but the mark scheme says it should be 13.6
there are 2 hydroxides so times the concentration by 2
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thymolphthalein
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(Original post by Maham88)
there are 2 hydroxides so times the concentration by 2
I forget that every time! Thank you.
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Maham88
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#997
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#997
do we need to know anything about dilution of an alkali ?
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thymolphthalein
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(Original post by Maham88)
there are 2 hydroxides so times the concentration by 2
Oh and if it was say, H2SO4 for example, would we multipy the concentration by 2 when finding the pH for it as well?
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bbyturtlexox
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(Original post by Maham88)
do we need to know anything about dilution of an alkali ?
no
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Maham88
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(Original post by thymolphthalein)
Oh and if it was say, H2SO4 for example, would we multipy the concentration by 2 when finding the pH for it as well?
yes
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