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Aqa chem 4/ chem 5 june 2016 thread

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Original post by 09ekennedy
-135.0 KJ mol-1


i got that
Original post by rwehy
**** was it 50 degrees celcius or kelvin for the enthalpy/entropy one?


50 degrees C
Original post by ManOfJustTin
Did anyone else pick sulphur for X?
I'm such an idiot 😂😂😭

Still such an easy paper I'm so happy


I did, then changed it last minute.

Original post by emsieMC
I think it was h2so4, that's what I put

I put that too. Pretty sure thats whats written in the book
Original post by thehollowcrown
Does the pressure have an effect on the emf? I said the emf increases eqbrm shift blah blah, but wasn't sure on that


Yeah I said it increased emf because position of eq shifts to side with less mols favoring reduction.


Know I mucked up on the calc question, I couldn't do it :frown: Can't remember what I put for the solubility question, I know I wrote about equilibria but I'm scared I wrote solubility increases :/

And the born haber wtf....May have messed up on that too.

All in all, much better than unit 4.
Original post by 09ekennedy
-135.0 KJ mol-1


I got - 67.5 because I halved my values beforehand as 2 moles of product were being formed. Standard enthalpy of formation by definition is the formation of 1 mole of a compound.

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Original post by RefusedAccess
Question stated that solubility is defined as the amount of solid able to dissolve in water, so as it is an endothermic reaction, more MgCl2 is produced if you increase temperature, hence solubility is increased


It said use your answer from the question above.

The answer was negative, hence the forward reaction is exothermic.

This same question (but with a different compound) came up in a previous paper.

Original post by Ejsjwwj
What did everyone get for delta G


-65.1 (divide it by 2 because it's standard meaning one mole, not two as question gave)
(edited 7 years ago)
Original post by ManOfJustTin
Did anyone else pick sulphur for X?
I'm such an idiot 😂😂😭

Still such an easy paper I'm so happy


I did!! You are not alone but it was only like 2 marks so don't worry about it if I were you!
Original post by ManOfJustTin
Did anyone else pick sulphur for X?
I'm such an idiot 😂😂😭

Still such an easy paper I'm so happy


I did, then changed it last minute :biggrin:

Original post by emsieMC
I think it was h2so4, that's what I put

I put that too. Pretty sure thats whats written in the book

Original post by thehollowcrown
Does the pressure have an effect on the emf? I said the emf increases eqbrm shift blah blah, but wasn't sure on that


Yeah I said it increased emf because position of eq shifts to side with less mols favoring reduction.


Know I mucked up on the calc question, I couldn't do it and I thought it was 5 marks but then my friend was like lol no so I've lost alot there :frown: Can't remember what I put for the solubility question, I know I wrote about equilibria but I'm scared I wrote solubility increases :/

And the born haber wtf....May have messed up on that too. Was it always 2K or what? Because thats what I ended up putting and for the calc for the cycle did everyone multiply the atomisation and ionisation energy of K by 2?

All in all, much better than unit 4.
I picked sulfur . Phosphorus or sulfur was fine
i got 2328 for born harbour cycle, 90 x 2 for atomisation of k and the 418 X2 for 2 ionisation energies for K
Nice easy paper. But I have made so many silly mistakes I just can't see myself doing very well. It's extremely itritating
Original post by thehollowcrown
50 degrees C

Needed converting to kelvin so 323
Original post by JammyW15
I got the same as you originally but when I went back, I forgot to multiply the ionisation Enthalpy by 2 and that's how I got 2000 something so I'm sure you didn't multiply it by 2


What? why did you multiply the ionisation enthalpy by 2? It was only the first ionisation energy?
Original post by Abbie122
You couldn't put sulphur is specifically said sodium to phosphorus only


Crap

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Original post by jenmturner
I did!! You are not alone but it was only like 2 marks so don't worry about it if I were you!


same hahaha, wish they'd just make it clear - 'give the name of an element other than sulphur that...' so annoying
I thought the one with delta g said for this reaction rather than for the production of 1 mole of SO3
You reckon 80/100 wud be an a???
Original post by 09ekennedy
-135.0 KJ mol-1


I don't think this is right, answer should be half of this I believe due to the mole ratio given in the equation.
H -196 kJ mol-1
S -189 K J mol-1
G -135 kJ mol-1

Btw what is the sign from answer -189 K J mol-1 indicates about the product relative to the reactants?
I put P then changed to S WOW 😓😓


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Nooooooooo I made too many silly mistakes. But all in all I think I definitely made up for chem 4 :biggrin:


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