The Student Room Group

Aqa chem 4/ chem 5 june 2016 thread

Scroll to see replies

My dumb ass did mno4 with fe 2+ smh rip 7marks LOL...Ive failed


Posted from TSR Mobile
Original post by 26december
Plot a graph of concentrations and absorption rates using known concentrations of KMnO4
Then set up colorimeter and place unknown sample and see what it's absorption rate is
Use the absorption rate on the graph and go across until you find the concentration

Something like that haha


Posted from TSR Mobile


Yessss :biggrin: I basically wrote that, just wasn't sure whether that's what they were looking for at the time aha.


Posted from TSR Mobile
Original post by zahraaj1
was the enthalpy of solution positive or negative


Negative something like -155 kjmol-1


Posted from TSR Mobile
Original post by olivia7001
Oh did no one write it in terms of entropy? I thought solubility increased because I worked it out with the Gibbs free energy


Yeah i did as well :/ but i think it's wrong because the delta g value doesn't affect the rate of the reaction ? idk
what did everyone's graph look like for the hydrogen fuel cell?
What was the mass people got for the C2O42- ions in 250cm3 solution?


Posted from TSR Mobile
I said solubility incrases then decreases, if I got the explanation right I should get 2 marks ? Not CE 0/3 surely
For the hexaqua complexes questions, there was something like cr(h20)6 3+ going to X(g) and Y(s). What was X(g). CO2?
Original post by lahigueraxxx
what did everyone's graph look like for the hydrogen fuel cell?


Straight horizontal line?


Posted from TSR Mobile
Reply 2469
Original post by mr.purplelambkin


I got like 88. Don't know where I went wrong what did u do
Original post by 26december
Plot a graph of concentrations and absorption rates using known concentrations of KMnO4
Then set up colorimeter and place unknown sample and see what it's absorption rate is
Use the absorption rate on the graph and go across until you find the concentration

Something like that haha


Posted from TSR Mobile


Said something very similar :smile:
Original post by Cadherin
So you get your 5:2 oxalate to manganate ion ratio by combining half-cell equations.

Then you divide moles by three because it was a trimolar potassium iron oxalate compound reacting.

Then you get mass by multiplying by Mr.

Then you do % purity and get 94.4%.


Good shout. How many marks of 7 do you reckon would be obtained if the divide by 3 part is missed out, to give a % purity of 35.33 (what i got)?
Reply 2472
Original post by Kay Fearn
What did people say for effect of increasing pressure on emf


I said increase as would be a in increase rate of reaction - I don't think reaction was reversible so le chateliers principle would be irrelevant? May be wrong


Posted from TSR Mobile
Original post by OloMed
For the hexaqua complexes questions, there was something like cr(h20)6 3+ going to X(g) and Y(s). What was X(g). CO2?


[Cr(h20)3(oh)3](s)


Posted from TSR Mobile
Any idea how many marks I'd lose for getting delta G as -135000? I multiplied delta H by 1000 so delta H and delta S were in the same units :'(
Original post by ManOfJustTin
Did anyone else pick sulphur for X?
I'm such an idiot 😂😂😭

Still such an easy paper I'm so happy


I did I'm such an idiot!!:frown: how many marks was that question?
Original post by Jonnyss
was the second one Na and not Na2O then?


nah second one asked for the reaction of the element (so Na + H2O) & the first asked for the reaction of the oxide of the element (P4O10 + H2O). i think
Reply 2477
Original post by DDan123
What did people put down for the last question about colorimetry?


Posted from TSR Mobile


It was 3 marks so I put:

MnO4- ions are purple
Filter light so only frequencies absorbed by the sample are let through.
The more concentrated the solution is, the less light it will let through.
Plot calibration graph with known concentrations and their absorbances. Use line of best fit to find concentration.

Posted from TSR Mobile
what do you think grade boundaries for A* will be? 84 last year, I am thinking 86 this year
Original post by hi-zen-berg
Good shout. How many marks of 7 do you reckon would be obtained if the divide by 3 part is missed out, to give a % purity of 35.33 (what i got)?


I got an answer for 35% too :frown:


Posted from TSR Mobile

Quick Reply