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Aqa chem 4/ chem 5 june 2016 thread

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Original post by 26december
I've got a different one...
I have:

Al(H2O)3(OH)3 + OH- --> [Al(H2O)2(OH)4]- + H2O

..... :/


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That's the right one!
Original post by Boundless_x
I've seen this one in pastpapers


This one is in my notes...

Which one are we supposed to use?


Can I see the past paper where this was???
Any predictions for topics tomorrow?
Original post by Lilly1234567890
yeah that what i meant- as when the +2 metal reacts with little hydroxide isnt that^ the equation we use?


Oh sorry, yep that equation
Reply 2204
Avatar for GO97
GO97
8
Original post by Lilly1234567890
what else apart from potassium nitrate can you use?


ive seen kcl
Original post by study2016
Guys - if you would recommend I do any 3 CHEM5 papers, which ones would they be? Very short for time - hectic exam timetable :s-smilie:


June 12
Jan 13
June 10

Original post by Lilly1234567890
why topics from AS are you guys looking back at?


None
Original post by Lilly1234567890
what else apart from potassium nitrate can you use?


KCl, NaCl, Na2SO4

you have to pick one which won't react with either the electrode or the solutions by the the electrode and will allow ions to move across them
Guys this is the mark scheme from 2011 ImageUploadedByStudent Room1466545580.639737.jpg
Reply 2208
Avatar for GO97
GO97
8
Original post by Boundless_x
I found June 2012 pretty hard


yeah june 12 wasnt great for me either but most of the marks were lost becasue i hadnt learned the colours for metals and the equations (i have now) i got 66 i think 64 was a B. there was this big 12 mark equation/colour questions that tore me a new one
Original post by werdo1997
Does anyone know the general method of calculation when you have to use the specific heat capacity of water and the mass of something?


You would use the equation
Q= mass of water ×temp change × specific heat capacity ... I believe :smile:

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Original post by werdo1997
Does anyone know the general method of calculation when you have to use the specific heat capacity of water and the mass of something?


I saw a question to work out the temperature change when you dissolve something in water.

They give you the delta H so to get q you multiply delta H by 1000 and the number of moles of the thing you dissolved in water (they give you the mass so you divide it by the reactants Mr to get the moles). Then you rearrange q=mcdeltaT so you divide q by the mass of the water and the specific heat capacity.
http://www.thestudentroom.co.uk/attachment.php?attachmentid=52079&d=1209931865

Just checking if these are all the colours we need to know and if they are correct?
Does anyone no the link between decreasing and increasing temperature on delta s or g ? In one paper it says decreasing temp makes delta g negative but then another says increasing temp delta g becomes negative. I could be way off with these statements. If anyone could simplify this id appreciate it ! :smile:


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Original post by SirRaza97
Can I see the past paper where this was???


It was Jan 11 q 6b
Original post by Hopefulmedic15
Guys this is the mark scheme from 2011 ImageUploadedByStudent Room1466545580.639737.jpg


Hmmm I see
Does it have anything on the right hand side like "allow just 1 OH-"
Because tbh I've learned just 1 OH in excess and that's what all the books say so I'm gonna stick with that.
Also I guess as long as there's as increase in OH-'s I'm sure they'll mark it correct as it's still an excess


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guys, how do you figure out which the positive/negative electrode is?
Original post by Humza Ali
guys, how do you figure out which the positive/negative electrode is?


Oxidation always happens at the negative electrode aka the reducing agent.


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Original post by Sexybadman
Does anyone no the link between decreasing and increasing temperature on delta s or g ? In one paper it says decreasing temp makes delta g negative but then another says increasing temp delta g becomes negative. I could be way off with these statements. If anyone could simplify this id appreciate it ! :smile:

increasing the temp makes T#S bigger therefore it makes #G smaller

#G = #H -T#S
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Btw guys when calculating emf is it always the reduced one minus the oxidised one ?


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Original post by GO97
yeah june 12 wasnt great for me either but most of the marks were lost becasue i hadnt learned the colours for metals and the equations (i have now) i got 66 i think 64 was a B. there was this big 12 mark equation/colour questions that tore me a new one


Now that I think about it... That was probably the main reason why I struggled too since June 2012 is the one I started off with :tongue: I only got 70 in that paper but the ones I did after that I got into the 80s, thank god. 2015 paper was really good, hope tomorrow will be the same *prays*

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