Aqa chem 4/ chem 5 june 2016 thread

Just to point out that the enthalpy change of -198 kj mol-1 still needs the 'mol-1' section to it, because that's the units for enthalpy change. Using 'mol-1' as an argument to justify dividing by 2 is a fallacy because mol-1 is not referring to 'per mole of SO3', it purely denoting 'per such reaction' which is in this case forms 2 moles of SO3

50 degrees to 323 kelvin

Lets get this straight
1 mark for equation 2:5 ratio
2nd mark for no of moles of Mno4- 0.02x(26.4/1000)
3rd mark for finding moles of C2o4- using the ratio 0.00132
4th mark for x10 to find in original 250 cm3
5th mark for x by 88 Mr of C2O4 to get 1.16 as this is specifically for the total C2o4 present before titre so up to this point definitely right
6th mark for the Mr of C2o4 which is 88
7th mark for dividing by 2.29 or something then times 100% to get the percentage as 50.7
Here are the official 7 marks for this question as both the 50.7 and 94.4% answers concern C2o4 pressent in the original sample 94.4 gives 8 marks whilst this is a 7 marker so why isnt this paper out of 101 dalmations

Was there a question about advantage and disadvantage?? I don't remember that at aII?

Would I lose marks for not having my coordinate bonds as arrows? I drew them like normal covalent bonds and now I'm kicking myself!

It was the last question of the fuel cell one! 'What is the main environmental advantage of fuel cells' or something

How many marks do you reckon I'll lose for not dividing the enthalpy/entropy equation by 2? I think there were 6 marks available, not sure

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I said they don't need to be electrically recharged but apparently it's that they don't produce CO2

However the last part of that question was about them not being carbon-neutral.

My bad, meant second to last question*
Yeah its either acid rain or no co2 emission as the question said 'environmental advantages'

Guys for the Lattice dissociation question did you have to times the 90 which was atomisation of K by 2??

If my reaction was endothermic do I get follow through marks for correct explanation?

Last question is referring combustion of fossil fuels releasing CO2



Yes.

Normally do

Last question is referring combustion of fossil fuels releasing CO2



Yes.

Normally do

Is that all you had to do? I got 1910kjmol-1 or something

Ahh fair enough i do see :/. However for the reaction you had 2 moles of SO2/SO3, therefore when you do the eqtn, in terms of units, a 'KJ mol-1' is multiplied by 'mol' (the 2 as there are 2 moles of SO3/SO2) therefore delta H is in KJ but for one mole you divid by 2 again to get KJ mol-1? sorry for complex stuff

Yeah, just realised that I made a tiny mistake, forgot to remove 4s first due to lower energy compared to the 3d... :/