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Equilibria, Energetics and Elements (F325) - June 2011 Exam.

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Original post by TsunKit
Could someone explain to me why the second electron affinity is +'ve. I think it was something to do with removing a negative charge?
It'd be nice to have someone clarify though :smile:


Sorry i meant to say endothermic.
Original post by HHPP
A lot of energy needed means it's endothermic.


yes sorry, slip of the keyboard.
Reply 1662
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susan23
3
Original post by Perky perks
so which one is it that is like a born haber cycle but uses hydration and solution instead of atomisation and ionisation??


you make a born haber cycle to find the enthalpy of solution by using the lattice enthalpy and the hydration enthalpys.
Reply 1663
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mandn
Original post by susan23
wtf is half neutralisation :lolwut: :frown:


When you have say 1 mole of acid and half a mole of base, it then leaves you with half a mole of acid, half mole of it's conjugate base and water, it is a method for creating buffer solutions
Original post by SteveScott
It can't hurt, just rememberit's used in detergents, it's a pretty general answer to 'what is this chemical used for' in chemistry exams :biggrin:


Ok, though i doubt i can really fit anything else in my ridiculously tiny brain right now :sigh:

Original post by susan23
wtf is half neutralisation :lolwut: :frown:


This :banghead:
Lone pairs on ligands when drawing complexes?????
Original post by SteveScott
It can't hurt, just rememberit's used in detergents, it's a pretty general answer to 'what is this chemical used for' in chemistry exams :biggrin:


Its also used as a chelating agent.
Reply 1667
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susan23
3
Original post by mandn
When you have say 1 mole of acid and half a mole of base, it then leaves you with half a mole of acid, half mole of it's conjugate base and water, it is a method for creating buffer solutions


WHAT THE ****!!! I DIDNT KNOW THAT!! looooooooooooooooooool

so what happens to the other half of the acid then??? reacts to form water?
Original post by INeedToRevise
Lone pairs on ligands when drawing complexes?????


Don't think so....
what is the tetrahedral complex and what are the bond angles?
I'm confused, when deltaG<0, the reaction is spontaneous and hence stable, but in the mark scheme of the jan 11 paper it says deltaG>0 is stable. Why is this?
(edited 12 years ago)
Reply 1671
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susan23
3
Original post by INeedToRevise
Lone pairs on ligands when drawing complexes?????


yes I do...I dont htink theres anything wrong with it :smile:
Question 1A iii on the specimen paper

can someone tell me WHY they've divided 1x10-12 by 4?

pretty please :smile:
Original post by mandn
At half neutralisation [A-]=[HA] so Ka=[H+] so pKa=pH BUT ONLY FOR HALF NEUTRALISATION


^^ do we need to know that?? :s-smilie:
Reply 1674
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asem93
Reactions involving Complex ions:

- Percipitation
- Substitution
- Redox

Any more?
Reply 1675
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susan23
3
Original post by 123trident
I'm confused, when deltaG>0, the reaction is spontaneous and hence stable, but in the mark scheme of the jan 11 paper it says deltaG<0 is stable. Why is this?


nooooooooooooooooo!!!

delta G has to be below 0 so negative value for reaction to be feasible and spontaneous!!

OK ALWAYS REMEMbER THIS!!!
:biggrin:
Reply 1676
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asem93
Original post by KnuckleheadNinja
Question 1A iii on the specimen paper

can someone tell me WHY they've divided 1x10-12 by 4?

pretty please :smile:


THIS!
Reply 1677
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mandn
Original post by susan23
WHAT THE ****!!! I DIDNT KNOW THAT!! looooooooooooooooooool

so what happens to the other half of the acid then??? reacts to form water?


half a mole of acid reacts with half a mole of a base this then forms it's conjugate base and water, but when using a whole mole of acid and half a mole of base half a mole of acid doesn't react and forms a buffer with the half mole of it's conjugate base
Can someone plz clarify the lone pairs bit either way? As far as i remember you're not expected to draw them, in the past papers? xD
Reply 1679
Avatar for asem93
asem93
Original post by susan23
nooooooooooooooooo!!!

delta G has to be below 0 so negative value for reaction to be feasible and spontaneous!!

OK ALWAYS REMEMbER THIS!!!
:biggrin:


Susan did you get my message earlier?

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