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Aqa chem 4/ chem 5 june 2016 thread

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Original post by Hannahbram
How many marks would i lose for getting 50% not 94%? I forgot to times c2o4 moles by 3..


You divide c204 moles by 3
that test man fhuuuuck
Original post by Suits101
It wanted standard enthalpy change, hence you do it for one mole hence you divide answers by 2 I believe.


ohh really??
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

Was X the one that formed an acid? If so I did S too
Was the ratio 2:5??
Original post by Suits101
It wanted standard enthalpy change, hence you do it for one mole hence you divide answers by 2 I believe.


I remember thinking that and was unsure about whether to divide, so I just left it undivided and did the calculation that way
Original post by lahigueraxxx
Completely ****ed up the born haber cycle, honestly no idea how or why I got +1910 or something :frown: Stupid mistakes


i got that too
Are you sure its wrong?
Original post by lahigueraxxx
Completely ****ed up the born haber cycle, honestly no idea how or why I got +1910 or something :frown: Stupid mistakes


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
did anyone get +2404 or something for born haber?
What did everyone get for delta G
Reply 2370
Original post by vinchy
Purity 50.7 anyone?


Yes i got around that! I think quite of few have :smile:
Original post by GiveShekels
i got that too
Are you sure its wrong?


I got it too :/
Original post by Suits101
It wanted standard enthalpy change, hence you do it for one mole hence you divide answers by 2 I believe (that's what happened on a previous mark scheme)


I'm pretty sure it just asked for the enthalpy change for the reaction, and they provided you with the standard enthalpy changes for 1 mole, so I think you had to multiply the values by 2 not divide by 2.
Original post by Suits101
Hi I have some questions and answers if anyone wants to add to it?

Lattice dissociation of K2O being less endothermic than Na2O:

K+ ions are bigger than Na+ ions
Weaker electrostatic force of attraction between K+ and O2- ions/weaker ionic bonding
Less energy needed to break the ionic lattice

Solubility of MgCl2 decreases
Forward reaction is exothermic
Equilibrium shifts left to oppose increase in temperature

Enthalpy of solution = -155 kJ/mol


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
(edited 7 years ago)
Original post by emsieMC
I remember thinking that and was unsure about whether to divide, so I just left it undivided and did the calculation that way


did it specify for the formation of one mole?
Original post by Ejsjwwj
What did everyone get for delta G


-135.0 KJ mol-1
Original post by Suits101
Hi I have some questions and answers if anyone wants to add to it?

Lattice dissociation of K2O being less endothermic than Na2O:

K+ ions are bigger than Na+ ions
Weaker electrostatic force of attraction between K+ and O2- ions/weaker ionic bonding
Less energy needed to break the ionic lattice

Solubility of MgCl2 decreases
Forward reaction is exothermic
Equilibrium shifts left to oppose increase in temperature

Enthalpy of solution = -155 kJ/mol


for the lattice dissociation question i put na+ ions were smaller and that there is a stronger attraction between the molecules, would i still get the marks???
Unofficial mark scheme?
Reply 2378
**** was it 50 degrees celcius or kelvin for the enthalpy/entropy one?
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


You couldn't put sulphur is specifically said sodium to phosphorus only

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