The big giant AQA CHEM5 thread!!! (May/June 2013) Watch

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laurawoods
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#141
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#141
(Original post by SDavis123)
If I'm honest I actually have no idea but maybe someone else knows but I really doubt we'd get asked something like that so I doubt you need to worry too much about that

I'm presuming electrode potential is the same as emf which is a measure of something's ability to donate electrons
Hello, pls can I ask u a quick question about aqua ions?

You know the hydrolysis reaction whereby the metal aqua ions will form metal hydroxides, can this happen in water or do we need to add OH- nucleophile (by NaOH etc). Or does the ppt form by using only water in excess?
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SDavis123
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#142
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#142
(Original post by laurawoods)
Hello, pls can I ask u a quick question about aqua ions?

You know the hydrolysis reaction whereby the metal aqua ions will form metal hydroxides, can this happen in water or do we need to add OH- nucleophile (by NaOH etc). Or does the ppt form by using only water in excess?
Someone answered your question before and said that you could use either
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laurawoods
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(Original post by SDavis123)
Someone answered your question before and said that you could use either
oh cool sorry ...i didn't see the answer!
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laurawoods
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(Original post by SDavis123)
Someone answered your question before and said that you could use either
Hello pls can I ask u another very quick question:
In the chem5 revision guide from collins there is section on 'melting (fusion)' and 'boiling (vaporisation)' under the thermodynamics section. what do we have to know about these
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SDavis123
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(Original post by laurawoods)
Hello pls can I ask u another very quick question:
In the chem5 revision guide from collins there is section on 'melting (fusion)' and 'boiling (vaporisation)' under the thermodynamics section. what do we have to know about these
first time I've ever heard about that could be there just using different terminology or could be referring to an old/ diffferent spec, have a look at our spec and see what it says

Edit: Actually, it's not the first time I've heard about it, I've also heard about it in physics where deltaH= QmcdeltaT + ml but I don't think that's relevant to us here
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Fortitude
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#146
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(Original post by laurawoods)
Hello pls can I ask u another very quick question:
In the chem5 revision guide from collins there is section on 'melting (fusion)' and 'boiling (vaporisation)' under the thermodynamics section. what do we have to know about these
Not sure, could it just be that entropy increases during these processes? :dontknow:
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SDavis123
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(Original post by Seb Hudson)
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Mate I've just realized the you made a mistake in your table of the coloured ions.

You put, [Fe(H2O)6]^3+ is purple when it's actually pale brown (See top of page 238 - test for iron ions - Nelson Thornes)

Edit: I also found a bit of a sneaky question asking the colours of

Cr2O7^2- (orange or when reduced green - cant remember what the reduced version is :/ )

Cr^3+ (ruby)

MnO4^- (purple)



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BobLoblawLawBlog
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#148
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Can someone explain how changing the concentration of a substance affects the emf of a cell. e.g. how does decreasing the concentration of Mg^{2+} affect the emf of the cell Mg_{(s)}|Mg^{2+}_{(aq)}||Fe^{2+}  _{(aq)}|Fe_{(s)}
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erniiee
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#149
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#149
(Original post by SDavis123)
Mate I've just realized the you made a mistake in your table of the coloured ions.

You put, [Fe(H2O)6]^3+ is purple when it's actually pale brown (See top of page 238 - test for iron ions - Nelson Thornes)

Edit: I also found a bit of a sneaky question asking the colours of

Cr2O7^2- (orange or when reduced green - cant remember what the reduced version is :/ )

Cr^3+ (ruby)

MnO4^- (purple)

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According to the nelson thornes textbook, the colours of [Fe(H2O)6]3+ can actually be purple yellow or brown. IIRC, it's the hydroxide formed that is brown.

The partially reduced version of the dichromate ion is the green chromium(III) ion - Cr3+. In theory it should be ruby in solution, but impurities cause it to be of a green colour.
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Vip3rgt9
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#150
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Apparently we need to know colour changes of Transition metal chloride ions, I didn't even realise this...
The trouble with chemistry is that you need to remember colour changes from previous modules, which of course I forget as soon as I do the exam and when I need to re-learn them it hard to find the necessary resources to do so.

Also we need to re-learn the metal extraction equations.
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erniiee
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(Original post by Zazuwaved)
Not the best... I promise I will actually scan them tonight or tomorrow latest

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Hey, any chance you could scan those sheets?
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TBBT
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Hi everyone!! I was just looking through the AQA book and I'm over the moon because theres not much there!! that being said its probably really hard!! haha
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Zazuwaved
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(Original post by erniiee)
Hey, any chance you could scan those sheets?
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Quite difficult to scan since it was laminated, i hope they are readable , completely forgot to upload them
Attached files
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erniiee
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#154
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(Original post by Zazuwaved)
Name:  transmetal11.jpg
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Quite difficult to scan since it was laminated, i hope they are readable , completely forgot to upload them
Thanks so much, you're amazing!
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Zazuwaved
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(Original post by erniiee)
Thanks so much, you're amazing!
No problem :yep:

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Dirtybit
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#156
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#156
(Original post by Vip3rgt9)
Apparently we need to know colour changes of Transition metal chloride ions, I didn't even realise this...
The trouble with chemistry is that you need to remember colour changes from previous modules, which of course I forget as soon as I do the exam and when I need to re-learn them it hard to find the necessary resources to do so.

Also we need to re-learn the metal extraction equations.
Which module have you done colour changes in before? :confused:
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popnit
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(Original post by Zazuwaved)
Name:  transmetal11.jpg
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Size:  338.5 KBName:  transmetal2.jpg
Views: 237
Size:  165.4 KB

Quite difficult to scan since it was laminated, i hope they are readable , completely forgot to upload them
Thanks v much for these. Just one thing though, we don't need to know about silver

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king101
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(Original post by Zazuwaved)
No problem :yep:

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Thanks for those! There really good! One thing I have to ask...is this ALL AND EVERYTHING of colour changes we have to learn/memorise?

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Dirtybit
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#159
(Original post by popnit)
Thanks v much for these. Just one thing though, we don't need to know about silver

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You do need to know about silver
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Zazuwaved
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#160
(Original post by king101)
Thanks for those! There really good! One thing I have to ask...is this ALL AND EVERYTHING of colour changes we have to learn/memorise?

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As far as I know, yes. Best to check with ur chem teacher is possible because the spec is quite vague on this. this site's probably already been mentioned on this thread but alevelchemistry.co.uk might give you some more info.
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