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AQA CHEM5 A2 Chemistry - 19th June 2013

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Original post by Beth_L_G
I do aswell. My memory isn't good enough to learn them


Even if it was, I wouldn't trust it :biggrin:
Original post by megsy14
Could someone kindly link me the jan 13 mark scheme? it would be much appreciated :smile:


6 posts up :smile:
Original post by bananarama2
Am I the only person that derives the half equations each time?


It's safer that way. Better to know how to do it and spend a couple of minutes writing it out then going blank in an exam and been screwed. IMO, anyway.
How do you make an ionic equation from a balanced equation?
can someone explain why when you add excess NaOH to [Al(H2O)6]^2+ you get [Al(OH)4]- instead of [Al(OH)6]3- ????
Reply 1745
Avatar for ZazDogg
ZazDogg
Original post by 16dan2life
Na- Yellow flame
Mg to Phosphorous- White flame and White fumes
Sulphur- Blue flame and choking gas

For the bits highlighted in bold, there are other acceptable answers.


Choking gas. I wonder who's actually going to write that.

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Original post by ZazDogg
Choking gas. I wonder who's actually going to write that.

Posted from TSR Mobile


Well it did get a mark in a past paper and if you've ever smelt it, you'd agree :biggrin:
Reply 1747
Avatar for Anshul91
Anshul91
anyone else think that this Jans paper was alot harder than previous past papers alot of sneaky questions!

Can someone clarify please, in regards to the atomisation of half Cl2 gas to 1Cl is this half the bond dissociation? If its Cl2 going to 2Cl is that equal to the bond dissociation? Having problems interpreting what to do when the molecules are different ie half, or 2. Thanks
Reply 1748
Avatar for AmyLH
AmyLH
10
Original post by Anshul91
anyone else think that this Jans paper was alot harder than previous past papers alot of sneaky questions!

Can someone clarify please, in regards to the atomisation of half Cl2 gas to 1Cl is this half the bond dissociation? If its Cl2 going to 2Cl is that equal to the bond dissociation? Having problems interpreting what to do when the molecules are different ie half, or 2. Thanks


I thought Jan was bad. I did way worse in that than any other paper. Going to go through that again later.

Atomisation is equal to half bond diss if it's a diatomic molecule (eg Cl2)
What othe rmolecules are diatomic? Other than Cl2 or F2
Reply 1750
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Anshul91
Also Jan 2013 Question 7 (c) why is the half O2 not doubled in the overall equation of the 2 half cells, really doesnt make sense as everything in the half cell was doubled cept the O2?
Reply 1751
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Anshul91
Original post by Beth_L_G
What othe rmolecules are diatomic? Other than Cl2 or F2


Halogens
Original post by livinglife24
What exactly is the formula to work out enthalpy of solution?
I don't get the Jan 13 paper, ques 2d :confused:


Lattice dissasociation + Hydration of both ions present in the solid ionic compound
In born haber cycles i thought if you wanted to find ΔHf the equation was ΔHa + ΔIE(Ca) + Δea + ΔHld = ΔHf
but on June 10, question 1 (b) (iii) you take away the ΔHlatticedissociation from the rest :confused: can anyone explain please ?
Reply 1754
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Anshul91
Original post by MrMeep2580
Lattice dissasociation + Hydration of both ions present in the solid ionic compound


but because its MgCl2 there will be 2 Cl- ions hydrated so you need times the -364 by 2 to get the hydrated Cl- ions, so damn sneaky.
Original post by MrMeep2580
Lattice dissasociation + Hydration of both ions present in the solid ionic compound


Is that always the equation? I got down from my teacher it could be Sum of hydration - sum of lattice formation...or sum of hydration + sum of lattice formation. It's so confusing :erm:
Original post by Anshul91
but because its MgCl2 there will be 2 Cl- ions hydrated so you need times the -364 by 2 to get the hydrated Cl- ions, so damn sneaky.


Yeah, I always forget about that. So annoying
Reply 1757
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Anshul91
Original post by livinglife24
Is that always the equation? I got down from my teacher it could be Sum of hydration - sum of lattice formation...or sum of hydration + sum of lattice formation. It's so confusing :erm:


no if they give you the lattive formation rather than the lattice disociation then you use:


enthalpy of solution = - lattive formation + sum of enthalpy of hydration.
Reply 1758
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Anshul91
Original post by livinglife24
Yeah, I always forget about that. So annoying


so what type of molecules are like that which have 'X'Cl2 do yo u know?
Original post by Anshul91
so what type of molecules are like that which have 'X'Cl2 do yo u know?


any group 2 metal

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