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# AQA AS Chemistry 7404/1 and 7404/2 - 27th May 2016 and 10th June 2016 watch

1. Overall ionic equation should be

IO(3) + 5I(-) + 6H(+) -> (1/2)I(2) + (3)H(2)0

Sorry I can't subscript or superscript, but anyways - you an just multiply the bottom equation by 5 - instead of trying to balance them to 10 electrons. You can still cancel out the five electrons from both equations anyway.

Then it's just matter of integrating what you have left on the equation.

And the Iodide ion should be oxidised, since the bottom electron shows it has lost an electron. It has done so by an oxidising agent, which means that that oxidising agent has been reduced itself and this is of course if you can see at the top equation is the Iodine in the IO(3) ion.
2. HI can anyone help me on how to work out percentage uncertainties ???? i have completely forgotten how to do so :/
3. percentage error = uncertainty over / reading

And then, multiply by 100 to get a percentage.

And remember when given a value of uncertainties and you make two readings, like for example you do a titration and read the initial volume off the burette to the final volume - you have to multiply the uncertainty by two, because you made two readings. If that makes sense.
4. (Original post by jessnrm)
percentage error = uncertainty over / reading

and then, multiply by 100 to get a percentage.

And remember when given a value of uncertainties and you make two readings, like for example you do a titration and read the initial volume off the burette to the final volume - you have to multiply the uncertainty by two, because you made two readings. If that makes sense.
thank u so much
5. guys does a change in concentration not affect the maxwell boltzman distribution?
6. (Original post by haes)
guys does a change in concentration not affect the maxwell boltzman distribution?
Maxwell Boltzmann distributions are in paper 2 not paper 1

and increasing the number of particles will make the area under the curve bigger for a maxwell boltzmann distribution so i think a change in conc does affect the curve
Any tips to remember the names of the shapes of molecules?
To learn them I just copied out each shape a bunch of times and it worked for me. Past paper qs on molecule shapes are good to. Good luck!
8. (Original post by Christie_xx)
Maxwell Boltzmann distributions are in paper 2 not paper 1

and increasing the number of particles will make the area under the curve bigger for a maxwell boltzmann distribution so i think a change in conc does affect the curve
Ah okay, i just find it weird how equilibria and kinetics were separated.
I was doing a past paper and it said that increasing the number of molecules will have no affect on the value of the most probable energy so it sounded like a change in concentration doesn't affect the curve. Thank you!
9. Organic chem is in paper 2 right?
10. (Original post by haes)
Ah okay, i just find it weird how equilibria and kinetics were separated.
I was doing a past paper and it said that increasing the number of molecules will have no affect on the value of the most probable energy so it sounded like a change in concentration doesn't affect the curve. Thank you!
Ahh yeah the activation energy, average energy and most probable energy will all stay the same because nothing changes on the x axis because the number of molecules is on the y axis
11. (Original post by rosemondtan)
Organic chem is in paper 2 right?
yeah it is
12. what does everyone think of the specimen paper?
13. In questions with calculations, and there is no specific space for you to write your answer in, if I write two answers will the examiner award the correct one or penalise a mark (assuming i don't make my answer clear)?
14. I'm literally so dead for tomorrow wtf why did I ever think I wanted to do something in medicine looooool... I feel like I let myself down like I've made o many notes but my motivation literally went downhill a few weeks before the exams...
15. (Original post by haes)
Ah okay, i just find it weird how equilibria and kinetics were separated.
I was doing a past paper and it said that increasing the number of molecules will have no affect on the value of the most probable energy so it sounded like a change in concentration doesn't affect the curve. Thank you!
It doesn't change the shape of the curve, only the area under it

The only thing that will change the shape of the curve is temperature
16. (Original post by Christina1999H)
This is the whole booklet..my teacher cut it down and printed it for us with only our AS practicals in, but the first practical (volumetric solution) is on page 64. Sorry I cant send you a digital copy of my version!

http://filestore.aqa.org.uk/resource...-7405-PHBK.PDF
It's fine thank you so much! Goodluck with your exam.
17. (Original post by haes)
Ah okay, i just find it weird how equilibria and kinetics were separated.
I was doing a past paper and it said that increasing the number of molecules will have no affect on the value of the most probable energy so it sounded like a change in concentration doesn't affect the curve. Thank you!
Hi my teacher said that the topics overlap and so knowing aqa they might ask some questions on kinetics as well as it overlaps with energetics.
18. Does second ionisation energy follow the same trend as first ionisation energy for period 3 apart from sodium?

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19. Has any got a link to the chem specimen set 2 papers - i need a digital copy fast - please anyone
20. is mass spec on the paper tomorrow?

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