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AQA CHEM5 A2 Chemistry - 19th June 2013

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just need to do the aluminium reactions and then we are done( my teacher has been making sure we do all the reactions in the lab for transition metals)
How's everybody feeling about this exam?
Chemistry is usually my worst subject but it's the only one I am tracking an A on and I'm actually quite looking forward to this above my other exams. Just not too great at the maths side of it!
Original post by ficharlton
Don't we just need to know the colours period 3 elements burn in oxygen for the periodicty section?

just need to know; sodium is yellow flame, sulfur is blue flame and all the others are bright white with the smoke of the oxide
Original post by SamEastie
just need to know; sodium is yellow flame, sulfur is blue flame and all the others are bright white with the smoke of the oxide


Thought so :smile:
Original post by SamEastie
we do need to know them


Haha yea I found out, I was only reading off the spec, but it was vague as usual


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Original post by SamEastie
just need to know; sodium is yellow flame, sulfur is blue flame and all the others are bright white with the smoke of the oxide


Actually, you do need to know the stuff about choking fumes and white powder, it's in one of the past papers. But It'll only lose you a few marks at the most.
Reply 886
Original post by Dalts
To be honest, the curriculums so small and the exams so big that its likely they'll be able to ask everything.


dont say that :backstab::banghead::bhangra::crazy::fallenangel::groovy::judge:

somebody pleaseee
and have people started revising for this yet? honestly :confused:
Reply 887
Original post by loknath
and have people started revising for this yet? honestly :confused:


Not really, will probably start after C4 and CHEM4 next week. Hoping to get as close to 120/120 in CHEM4 as possible so I can get a bit of leeway with CHEM5.

Bit worried I'm leaving it a bit late but oh well. I can make sure I'm well stocked with red bull and pull a few all-nighters if need be :tongue:
Reply 888
Original post by Extricated
you get the answer when delta g = 0 as t = 462.7, thus at 463 it will not be feasible, hence it is only feasible when t is less than or equal to 462.7 not 463, so they used 462 as a whole number.


isnt a reaction feasible if for the temperature deduced and above?

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Reply 889
Original post by SamEastie
no, mine is just the normal one you need to know


Theyre both correct. And both equations will be on the mark scheme.
Reply 890
Sorry if this has already been asked but can somebody please post how you work out the gradient question on June 2012 Q2? The mark scheme isn't helping!
Original post by AmyLH
Not really, will probably start after C4 and CHEM4 next week. Hoping to get as close to 120/120 in CHEM4 as possible so I can get a bit of leeway with CHEM5.

Bit worried I'm leaving it a bit late but oh well. I can make sure I'm well stocked with red bull and pull a few all-nighters if need be :tongue:


That's exactly my plan! glad to know I'm not the only one who does all-nighters , I was literally a zombie during exam periods :smile:
Reply 892
Original post by Electronbean
That's exactly my plan! glad to know I'm not the only one who does all-nighters , I was literally a zombie during exam periods :smile:


At 1am suddenly I get super productive. Last night I did 2 C4 papers and 2 Chem4 papers all between 1am and 5am. :tongue:
Reply 893
Original post by sophie15
Sorry if this has already been asked but can somebody please post how you work out the gradient question on June 2012 Q2? The mark scheme isn't helping!


I remember this question. It's a nightmare...the answer is not 0.1 or something? So 0.098 was the answer? Basically I can't understand why it isn't 0.1 but anyway.

its the change in X. So take 2 values of X. And the divide by change in Y.

Its simple if you know it. But I did get 0.1 doing this question. Still confused why it isn't.:-P I think you just need to take obscure X and Y values :-D
Original post by Gazfink
I remember this question. It's a nightmare...the answer is not 0.1 or something? So 0.098 was the answer? Basically I can't understand why it isn't 0.1 but anyway.

its the change in X. So take 2 values of X. And the divide by change in Y.

Its simple if you know it. But I did get 0.1 doing this question. Still confused why it isn't.:-P I think you just need to take obscure X and Y values :-D

You get 0.1 if you read the values wrong, I did and asked my teacher why and I'd read the values off the graph slightly wrong.
Reply 895
hey guys about the period 3 stuff we need to know, which paper is the one where we need to know about choking fumes and white smoke?

also if anyone can be arsed could you please write out the colours of flames we need to know and also which give a white powder and choking fumes etc? lol it would be much appreciated
Reply 896
Original post by idunnotbh
hey guys about the period 3 stuff we need to know, which paper is the one where we need to know about choking fumes and white smoke?

also if anyone can be arsed could you please write out the colours of flames we need to know and also which give a white powder and choking fumes etc? lol it would be much appreciated


i wrote them out on a previous reply. But I'll paste them here

Sodium...yellow flame...white powder
Magnesium...white flame...white powder
Alluminum...white flame...white powder
silicon...white flame...white powder
Phosphorous...white flame...white powder
Sulphur...blue flame...choking fumes produced.
Reply 897
Original post by Sherlockedd
You get 0.1 if you read the values wrong, I did and asked my teacher why and I'd read the values off the graph slightly wrong.


Yeah that's what my teacher said. But then he also did it and got 0.1. He thought it was just an unfair question really haha :-P
Reply 898
For those using the CGP A2-Level Chemistry revision guide:
My teacher and I have spotted a small error on page 78 titled 'Electrochemical Cells'

About halfway down the page in the blue box labelled 'Rechargeable Cells use Reversible Reactions':

-> At the moment
the cell diagram has the second PbSO4(s) and the PbO2(s) written in the wrong order. (As written- both sides of the cell are oxidations)

The cell diagram should read:

Pb(s) l PbSO4(s)
l l PbO2(s) l PbSO4(s)





-> Finally the lead (IV) dioxide is the cathode (as that is where reduction takes place) and the lead is the anode (where oxidation takes place). The statement at the top states them the wrong way around.

CGP have been contacted and they have said they will make sure it's corrected in the next edition.
Reply 899

1.

Copper(ii) ions oxidise iodide ions to iodine. The iodine produced can be titrated with standard thiosulfate solution, and, from the amount of iodine produced, the concentration of the copper(ii) ions in the solution can be calculated. The relevant equations for this process are given below:


2Cu2+(aq) + 4I-(aq) 2CuI(s) + I2(aq)
2S2O32-(aq) + I2(aq) S4O62-(aq) + 2I-(aq)
A sample of 4.256 g of CuSO45H2O is dissolved and made up to 250 cm3 in a volumetric flask. A 25 cm3 portion is added to an excess of potassium iodide. The iodine formed required 18.00 cm3 of a 0.0950 mol dm-3 solution of sodium thiosulfate for reduction. Calculate the percentage of copper in the crystals.

Someone help I calculated the answer as 50%. I don't have the answer but could some check to see if they get the same answer as me.

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