Equilibria, Energetics and Elements (F325) - June 2011 Exam.

Medicine offer bye bye. Didn't even complete the paper and am looking at a solid U/E

This is probably why the grade boundaries are so high:

OCR don't want to give in to pressure from the public to lower the grade boundaries, they don't want to show that if you complain and moan about an exam and get it in the newspaper etc. then that can determine the boundaries.

Instead to spite honest hardworking students they raise it even higher, to send a clear message back to future pupils.

Reply 3222

Unkempt_One

13

Original post by Kalamari Dave

1. Agreed with Unkempt. Just getting the answer would warrant at least 4 ish marks.
2. Disagree here. Buffers have an effective range of action within 1 pH unit of their pKa. Ethanoic acid (I think) had the closest pKa to the "magic pH" by quite a bit, so it would be the most effective buffer and the ideal acid for the sweet. Any acid can be concentrated specifically to produce the "magic pH", but the buffering action is the main requirement.
3. There are two versions of teh fuel cell equations, one involving OH- and the other involving H2O. If I remember correctly, the exam requied the OH- one? :dontknow:

4. Water should be fine I think.

Yeah, sorry, that makes sense. I wonder where in the textbook that obscure fact is raised because it's definitely not something which can be deduced. In that case, how do you think you were supposed to justify your choice of acid? I believe the question implied it wanted to see your reasoning.

(edited 12 years ago)

Reply 3223

dunnicare

12

Original post by TheUsername42

This is probably why the grade boundaries are so high:

OCR don't want to give in to pressure from the public to lower the grade boundaries, they don't want to show that if you complain and moan about an exam and get it in the newspaper etc. then that can determine the boundaries.

Instead to spite honest hardworking students they raise it even higher, to send a clear message back to future pupils.

Probably not.

Reply 3224

lollington-mccoy

10

OCR= overly cocky rankings; showed this to my mate doing chemistry at uni- he almost **** himself.... good luck for tomorrow. :smile:

Reply 3225

blush.ox

15

Original post by lollington-mccoy

OCR= overly cocky rankings; showed this to my mate doing chemistry at uni- he almost **** himself.... good luck for tomorrow. :smile:

thanks.

Reply 3226

BackDoorEntry

Original post by blush.ox

thanks.

Blush, I don't know what I'm going to do! I was already in a state before today, but now these grade boundaries have just taken the piss! I feel genuinely ill :frown:

Reply 3227

blush.ox

15

Original post by BackDoorEntry

Blush, I don't know what I'm going to do! I was already in a state before today, but now these grade boundaries have just taken the piss! I feel genuinely ill :frown:

BDE, rather not say the whole thing :tongue:

, same here i actually had a lil bit of hope before today, but now i've prty much died inside. I still cannot believe how high it is, some people must have done really well :colonhash:

. I dont want to face tomorrow and the consequences. Hopefully you'll be fine. I fail at chemistry, should've realised this along time ago :emo:

.

Reply 3228

BA1

6

The grade boundaries seem very fair to me... the biggest surprise is F321 though.... 44/60 for an A in January and now 49/60, that's a big jump. The AS people obviously improved a lot during the re-sit.

You might be surprised with F325 anyway... the mark scheme could be flexible as with the case of F324 in January. For example if you only circled one double bond in the F324 paper instead of both (even though they WOULD both react), you got the mark anyway.

So maybe in F325 you'll get marks for an educated guess to Magic Tang with workings showing you know the formulae, substitutions etc.

Reply 3229

Bambi111

Original post by cawse879

was wandering if someone could answer a couple of queries about some questions,

1- for the last questions, i didnt get any of the equations but got the 67.6%, will this be 6 marks assuming that each equation was worth 1?

2- could any acid be used for the buffers question becasue it didnt specify?

3- in the unofficial mark scheme there seems to be an oh- ion in the eqaution for the cell discharging, is this a mistake or have i missed something?

4- in Q2 writing the equation for step 1 i gave the other product as water not hydrogen gas as it says in the mark scheme, will this still be credited as the q didnt say hydrogen was made?

thanks in advance? :smile:

You had to use lactic acid, but I think you would have got marks for working out the others. Something about the pka and the pH of the buffer being close to each other.

EDIT: Considering it's suppose to be 80% for an A 72% is quite low, not as low as January but you don't know the mark scheme could have been leniant.

(edited 12 years ago)

Reply 3230

Kalamari Dave

Original post by Unkempt_One

Yeah, sorry, that makes sense. I wonder where in the textbook that obscure fact is raised because it's definitely not something which can be deduced. In that case, how do you think you were supposed to justify your choice of acid? I believe the question implied it wanted to see your reasoning.

True that. I think it was in one of those little "examiner tip" boxes or summin with little snippets of information.

Then again, since the grade boundary is so riduculously high, I think the question did want to see reasoning indeed.