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Hey can someone help me with this questions :

Why do have to filter zinc (reducing agent) during a vanadium experiment before potassium manganate ( oxidising agent) is added?? there is 3 or 4 marks involved with this question. can someone help?
Original post by FREYA2898
Hey can someone help me with this questions :

Why do have to filter zinc (reducing agent) during a vanadium experiment before potassium manganate ( oxidising agent) is added?? there is 3 or 4 marks involved with this question. can someone help?


is this on the empa exam??
Original post by chocolatte123
is this on the empa exam??


No sorry, I got this from a past paper question and was wondering what the answer is. I do ISA anyway :smile:
Hey is anyone here doing Chemistry 3X? This is the AS empa resit :smile:
Does anyone have a copy of last year's a2 ISA and EMPA with the mark schemes?
Original post by shiney101
Does anyone have a copy of last year's a2 ISA and EMPA with the mark schemes?


The mark schemes are now online I think on the AQA website not sure about the papers
how are people prepping for the 2016 chem6x paper?
I've done the a2 empa for bio and chem (aqa - bio6x and chem6x)
just got the as resit chem 3x left to do on Wednesday :wink:
Can someone help out in e (ii) ?
Original post by PlayerBB
Can someone help out in e (ii) ?


think about how much of the crystals would be dissolved at the start, and how much would still be dissolved when it is cooled down
Original post by samb1234
think about how much of the crystals would be dissolved at the start, and how much would still be dissolved when it is cooled down


Ahhh right, thank you!! :h:
Original post by 9307914
The mark schemes are now online I think on the AQA website not sure about the papers

I thought so too and they have the actual unit 4/5 etc papers but they don't have the ISA/empa papers and only have a mark scheme for task 1 of the empa :frown:
Reply 452
Original post by PlayerBB
Can someone help out in e (ii) ?


Well the ideal solvent is the one in which solute dissolves most in hot solution and doesn't dissolve in cold solution at all. Since no solution is ideal, we use the solution in which most solution dissolves most in hot solution and least in cold solution, as in the one with greatest difference in the two solubility values.
So now in this case, the difference in values of solution 1 is 5 whereas in solution 2 is 7.5 and as solution 2's difference > solution 1's difference so 2 is a better solvent.
Well i hope it was a helpful explanation :smile:
Original post by Aimen.
Well the ideal solvent is the one in which solute dissolves most in hot solution and doesn't dissolve in cold solution at all. Since no solution is ideal, we use the solution in which most solution dissolves most in hot solution and least in cold solution, as in the one with greatest difference in the two solubility values.
So now in this case, the difference in values of solution 1 is 5 whereas in solution 2 is 7.5 and as solution 2's difference > solution 1's difference so 2 is a better solvent.
Well i hope it was a helpful explanation :smile:


Thank you Aimen!!

Well actually I needed (ii) not (i) but thank you for the effort of explaining it :h:

And I figured out part (ii) now :smile:
Reply 454
Original post by PlayerBB
Thank you Aimen!!

Well actually I needed (ii) not (i) but thank you for the effort of explaining it :h:

And I figured out part (ii) now :smile:


Oops my bad :P
Reply 455
Hey, wondered if anyone could clear this up for me,

Going over past papers for Chem6x I've come across drawing graphs for the Iodine clock reaction a few times, usually pretty straightforward, log (1/t) is plotted on the y-axis and Log(volume) on the x-axis, but I noticed in the mark scheme that says a mark is lost if the y-axis is plotted with ascending negative numbers? I'm not sure if the wording is awkward but the y-values for Log91/t) are usually negative, it doesn't seem to make sense to plot them in a descending scale (i.e. negative values getting more negative going up the y-axis),

Cheers
Finding unit 5 difficult for aqa
Particularly the suggest questions of thermodynamics and redox.
Always get confused between oxidising and reducing agent.


Posted from TSR Mobile
Original post by Bloom77
Finding unit 5 difficult for aqa
Particularly the suggest questions of thermodynamics and redox.
Always get confused between oxidising and reducing agent.


Posted from TSR Mobile


Post the questions that you don't understand... :smile:
An oxidising agent itself gets REDUCED
A reducing agent itself gets OXIDISED
Reply 458
Chemistry exam day after tomorrow(toms bio) need so many prayers. I'm so worried...

can anyone give me a brief on carbon 13 nmr? its new in our syllabus and ur teacher....... by the way its Alevel
Reply 459
Original post by wb236
Hey, wondered if anyone could clear this up for me,

Going over past papers for Chem6x I've come across drawing graphs for the Iodine clock reaction a few times, usually pretty straightforward, log (1/t) is plotted on the y-axis and Log(volume) on the x-axis, but I noticed in the mark scheme that says a mark is lost if the y-axis is plotted with ascending negative numbers? I'm not sure if the wording is awkward but the y-values for Log91/t) are usually negative, it doesn't seem to make sense to plot them in a descending scale (i.e. negative values getting more negative going up the y-axis),

Cheers


I guess going through examiner reports and seeing their so-called perfect answers can help!

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