OCR Chemistry A F325 Equilibria, Energetics and Elements Wed 13 June 2012
Chemistry exam discussion - share revision tips in preparation for GCSE, A Level and other chemistry exams and discuss how they went afterwards.
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Re: OCR Chemistry A F325 Equilibria, Energetics and Elements Wed 13 June 2012No paper or actual unofficial mark scheme up and I doubt there is going to be one anytime soon(Original post by kimmey)
sorry ive been away for abit from this thread has there been a paper or an unofficial mark scheme posted yet ?
probably 1 for saying that it donates two pairs but the second is probably for the coordinate bonds.(Original post by otrivine)
will i get 1 or 2?
77-78 probably although I wouldn't be surprised if it's slightly higher. They convert it once they have calculated the grade boundaries so for example, if 77 was an A that would translate to 120ums.(Original post by lilac237)
so honestly and actually guys without saying oooh too high or too low, what do people think will be needed markswise out of 100 to get an A? but then how does it convert to ums that way?
ahh i know ive lost atleast 10 raw marks and thats just stuff i 10000% know i've got wrong, god knows how many other stuff there will be! -
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Re: OCR Chemistry A F325 Equilibria, Energetics and Elements Wed 13 June 2012LOL very true!(Original post by melissa1994)
Because people were struggling to finish apparently, but the hour paper is the F324 module not this one - this one the F325 was 2 hour up from 1 hr 45, but the same applies - people were struggling to finish so they decided to add extra time... Along with that they also increased all the grade boundaries because apparently "extra time means people will get higher marks"...... It's not as if the extra time makes us suddenly know more!!!
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Re: OCR Chemistry A F325 Equilibria, Energetics and Elements Wed 13 June 20127 marks between boundaries from A-C then 6 from C-D (based on January 2012) Eg 77-A 70-B 63-C 57-D(Original post by Schwepper2)
So if the grade boundary for an A is about 76-78, will the difference between grades usually be about 6 raw marks? For example, what would a C/D be in raw marks do u think?Last edited by myyrh; 16-06-2012 at 00:52. -
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Re: OCR Chemistry A F325 Equilibria, Energetics and Elements Wed 13 June 2012Actually wrote 'Hendersson Hasselbach' in the working out space STRAIGHT AWAY lol (Y)(Original post by pete clark)
henderson hasslebach equation FTW!!! -
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Re: OCR Chemistry A F325 Equilibria, Energetics and Elements Wed 13 June 2012I am(Original post by Yabdi1)
Anyone gonna sit the F324 on Tuesday?
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Re: OCR Chemistry A F325 Equilibria, Energetics and Elements Wed 13 June 2012For the buffer pH question i got half of the correct answer due to my concentrations, worked it out correctly too and put a single line through it. How many marks do you think i would still get thanks
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Re: OCR Chemistry A F325 Equilibria, Energetics and Elements Wed 13 June 2012maybe 4 marks(Original post by RoadRunner)
For the buffer pH question i got half of the correct answer due to my concentrations, worked it out correctly too and put a single line through it. How many marks do you think i would still get thanks
and for making the PH would i get the marks for saying adding a weak acid and conjugate base and said base is NaOh and the acid as the butanoic the one they said and said to minimse PH change? -
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Re: OCR Chemistry A F325 Equilibria, Energetics and Elements Wed 13 June 2012Been 71 and 72 in the past for an A in the two june papers.
Yes, this was easier but by the looks of things people made all sorts of random mistakes. The buffer, Kc, % purity, rate constant, charge on the ligand... That Co2 question was tricky also.
I reckon I have around 85 or 86...
Anyone think it will be about 76 for an A, 69 for a B, and so on..? The only reason I can't (and also hope haha) they don't raise is down to the amount of niggly mistakes people made. Anyone else agree? -
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Re: OCR Chemistry A F325 Equilibria, Energetics and Elements Wed 13 June 2012and for making the PH would i get the marks for saying adding a weak acid and conjugate base and said base is NaOh and the acid as the butanoic the one they said and said to minimse PH change?(Original post by nereik6794)
Been 71 and 72 in the past for an A in the two june papers.
Yes, this was easier but by the looks of things people made all sorts of random mistakes. The buffer, Kc, % purity, rate constant, charge on the ligand... That Co2 question was tricky also.
I reckon I have around 85 or 86...
Anyone think it will be about 76 for an A, 69 for a B, and so on..? The only reason I can't (and also hope haha) they don't raise is down to the amount of niggly mistakes people made. Anyone else agree? -
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Re: OCR Chemistry A F325 Equilibria, Energetics and Elements Wed 13 June 2012I got the buffer wrong one haha.(Original post by otrivine)
and for making the PH would i get the marks for saying adding a weak acid and conjugate base and said base is NaOh and the acid as the butanoic the one they said and said to minimse PH change?
But to make a buffer I wrote the acid(excess) reacts with NaOH to form sodium ethanoate and water. The sodium ethanoate then turns into Na+ and ethanoate ions. This then sets up and equilibrium with the butanoic acid. -
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Re: OCR Chemistry A F325 Equilibria, Energetics and Elements Wed 13 June 2012so am i correct you think?(Original post by nereik6794)
I got the buffer wrong one haha.
But to make a buffer I wrote the acid(excess) reacts with NaOH to form sodium ethanoate and water. The sodium ethanoate then turns into Na+ and ethanoate ions. This then sets up and equilibrium with the butanoic acid. -
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Re: OCR Chemistry A F325 Equilibria, Energetics and Elements Wed 13 June 2012It was out of 2 so I reckon you should get at least 1 mark tbh, chemistry isn't marked anywhere as harshly as physics.(Original post by otrivine)
so am i correct you think?
If you calculated the pH of the buffer as 4.12 you will most probably still score 3/5 due to the 'common errors' section.
What is your guess at the boundaries? -
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Re: OCR Chemistry A F325 Equilibria, Energetics and Elements Wed 13 June 2012oh yes why did some people get 4.12 and some 4.22?(Original post by nereik6794)
It was out of 2 so I reckon you should get at least 1 mark tbh, chemistry isn't marked anywhere as harshly as physics.
If you calculated the pH of the buffer as 4.12 you will most probably still score 3/5 due to the 'common errors' section.
What is your guess at the boundaries? -
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Re: OCR Chemistry A F325 Equilibria, Energetics and Elements Wed 13 June 2012I dunno the concentration they gave you at the beginning of the q you didn't use in the buffer equation for some reason, because they reacted or something.(Original post by otrivine)
oh yes why did some people get 4.12 and some 4.22?
How do you think you did? -
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Re: OCR Chemistry A F325 Equilibria, Energetics and Elements Wed 13 June 2012the way i calculated was to convert the cm3 into dm3 then used the formula of concentration to find the moles then i used the equation for buffers and got 4.something ??(Original post by nereik6794)
I dunno the concentration they gave you at the beginning of the q you didn't use in the buffer equation for some reason, because they reacted or something.
How do you think you did?
