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OCR Chemistry A F325 Equilibria, Energetics and Elements Wed 13 June 2012

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Can anyone explain question 2di? I totally don't get the point!!!! The examiner report says *Needs formation of co3- ions from C and O not breakdown of co3 2- ions. Don't understand why! Thanks :biggrin:

(f325 jan 2012)

(edited 10 years ago)

Reply 5181

AnharM

I really wanted an A* for Chemistry, I got 74 UMS in January for F324, and got full marks on coursework, so I need 136/150 UMS to get the A*, but I feel I can't achieve that. This unit is difficult because of the stretch and challenge questions. I really don't know where to start from in these hard questions, such as June 2011 paper, question 4 e) it asks you to deduce the chemicals required to prepare this buffer. In the mark scheme it just says 'chemicals are lactic acid and sodium lactate' without any working out. I don't understand how they got to that answer. Anyone care to help? And the last question also made me freeze. I hate this unit. Oh well, only need a D in this unit to get the A overall.

Reply 5182

mmasters

Quick question, do we have to know about Kp? Going through old questions and it keeps rearing its ugly head.

Reply 5183

gemmabug

Original post by mmasters

Quick question, do we have to know about Kp? Going through old questions and it keeps rearing its ugly head.

What on earth is Kp ?!?!

Reply 5184

amars94

The jan 2013 was rather tricky so hopefully this June paper will be better. In jan 70/100 was an A.

Posted from TSR Mobile

good luck everyone!

Does anyone know how to do feb 2012 question question 4 ii pls, need to go into this exam with confidence

****ty Exam

Horrific. Dreading results day now!

Reply 5189

neldee95

The last question was sent from hell.....

Reply 5190

Ashwin_Bhatt

Original post by neldee95

The last question was sent from hell.....

I got NiSO4.7H2O, think that was the right answer!

Reply 5191

mariomario1

Original post by Ashwin_Bhatt

I got NiSO4.7H2O, think that was the right answer!

I think that's the right answer i put NiCl2 . 7H20 instead cos i was running out of time but I got all the other working out right up to the point where the mass of the -2 ion was 96. Reckon I've lost one mark max or ?

(edited 10 years ago)

Reply 5192

DanielleCrow

That exam was horrific!! Did anyone know how to do that buffer Ph one? and I literally didn't have a clue about the last question, I managed to work out it had 7 H20 in it but how were you supposed to work out what the nickel(II) salt was??? :s-smilie:

Reply 5193

Liberty_Alice

Original post by DanielleCrow

I got NiS04.7h20
It was very tough, I got there somehow
Did anyone else get this answer?

Posted from TSR Mobile

Reply 5194

mariomario1

Original post by Liberty_Alice

I got NiS04.7h20
It was very tough, I got there somehow
Did anyone else get this answer?

Posted from TSR Mobile

That should be the right answer i remember working out the molar mass of the -2 ion was 96 and that fits in with S04. I put Cl2 though because I was running out of time and didn't have time to do the adding up and stuff. I worked out everything else though it's just the final bit where you have to give the formula. I hope I've only lost one mark for that.

Reply 5195

MediocreIguana

To work out the buffer, did you have to do that method where you take away the moles of base from the acid like in june 2012?

Reply 5196

daisyrchds

Original post by MediocreIguana

To work out the buffer, did you have to do that method where you take away the moles of base from the acid like in june 2012?

Yeah think so because one was in excess. Something like 3.99?

Reply 5197

MediocreIguana

Original post by daisyrchds

Yeah think so because one was in excess. Something like 3.99?

I think that's right, though I got something else

Reply 5198

Matt III

For the last question I put NiO6.7H20, Pretty certain it's wrong, O6 does have a mass of 96 but the charge on the nickel would have had to have been +12... Hopefully this is just 1 mark right?