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# OCR Chemistry A F322 Chains, Energy and Resources Wed 23 May 2012

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1. (Original post by TonyQuenca2012)
Yes I that's what I think as it was harder than June 2011 I made so many stupid mistakes like for the question about why ethene 1 2 diol was less volatile than methanol I said ethane 1 2 diol has hydrogen bonds where as methanol has weaker van fee waals forces but I didn't specify it has more hydrogen bonds due to the additional oh group do u think I'll get a Mark for that? It was worth 2 marks?
ahh that's cruel man! I'm not too sure mate! OCR are VERY specific they'll definitely be looking for the idead that ethan1-2 diol has more OH groups and so therfore more hydrogen bonding is formed! but lets hope you do
2. (Original post by abzman619)
ahh that's cruel man! I'm not too sure mate! OCR are VERY specific they'll definitely be looking for the idead that ethan1-2 diol has more OH groups and so therfore more hydrogen bonding is formed! but lets hope you do
How many marks do u think you have got?
3. (Original post by abzman619)
for the percentage yield question! did people use volume/24000 to find the molar calculations as the formula stated that they were all in gaseous state?
No, because you were given the amount in tonnes of the reactant (CH4) and product (H2).

Therefore you would of converted tonnes into mass (grams) and then used mole = mass/RFM.

1 tonne = 1x106 grams.

RFM of CH4 = 16
RFM of H2 = 2

Calculate theoretical:

The amount of CH4 used was 200 tonnes
200 x (1x106) = 20000000 grams.
Moles = Mass (200000000) / RFM (16 (12+4))
= 1250000 moles of CH4
The molar ratio of CH4 to H2 was 1:3
Therefore 1250000 x 3 = 3750000 moles of H2 produced Theoretically

Calculate Actual:

68.4 tonnes of H2 produced
68.4 x (1x106 ) = 6840000 grams of H2 produced
Moles = Mass (6840000) / RAM (2) = 3420000 Moles of actual H2 produced.

To calculate percentage yield we have to do actual (Moles) over theoretical (Moles) x 100

Actual = 3420000
Theoretical = 3450000

3420000/3450000 x 100 = 91.2
4. is their an unnofficial mark scheme for this?
5. (Original post by dench_crepz)
is their an unnofficial mark scheme for this?
yes, pg159
6. hey guys for the cracking question i was panicking and wasnt thinking straight. but i identified the right fragment as [c2h3]+ and th e cracking eqation as c12h26----->c3h8+c9h18 <-- i didnt split that to 3 propene molecules how many marks do you think ill get? 2/3?
7. (Original post by louisjevans)
yes, pg159

safe
8. Wt do u guys think the boundaries for an A will be do u think it may be 75/74 did anyone think it was harder than June 2011 and I think I got 70 at the least this should be a B definitely shouldn't it? Wt do u guys think u got?
9. (Original post by Theafricanlegend)
hey guys for the cracking question i was panicking and wasnt thinking straight. but i identified the right fragment as [c2h3]+ and th e cracking eqation as c12h26----->c3h8+c9h18 <-- i didnt split that to 3 propene molecules how many marks do you think ill get? 2/3?
Well it was 4 marks. 1 of the marks would have been for the correct equation. So you would get 2/4 or maybe 3 if you identified the alkene as propene.
10. (Original post by TonyQuenca2012)
Wt do u guys think the boundaries for an A will be do u think it may be 75/74 did anyone think it was harder than June 2011 and I think I got 70 at the least this should be a B definitely shouldn't it? Wt do u guys think u got?
i am not being rude ok but havent you ask this like x10 now?
11. (Original post by myyrh)
Well it was 4 marks. 1 of the marks would have been for the correct equation. So you would get 2/4 or maybe 3 if you identified the alkene as propene.
CANT believe it. such a stupid mistake
12. Just look at that unofficial mark scheme and there's a mistake with the Ethene combustion, should be C2H4 + 302 ---> 2C02 + 2H20
That is all
13. (Original post by dench_crepz)
safe
as safe as a chav in a locker
14. (Original post by Amz1217)
Just look at that unofficial mark scheme and there's a mistake with the Ethene combustion, should be C2H4 + 302 ---> 2C02 + 2H20
That is all
how can i get hold of the markscheme?
15. (Original post by narli)
how can i get hold of the markscheme?
pg 159
16. how many ums do people think is 86/100 ?
17. (Original post by kimmey)
how many ums do people think is 86/100 ?
Anything between mid 130s to mid 140s
18. I know a lot of people have been comparing this paper to the one in june 2011 but to anyone who's done the january 2012 paper do you think that paper was easier, harder, or about the same level as the one we've just sat ? Because a lot of people at my college were saying the one we've just sat was a better/easier paper (we did the january 2012 one as a mock) and I know for the paper last january the grade boundary was the highest it's ever been at about 83 out of 100 for an A. So now I'm worried that if people generally thought this paper was around the same level/easier it could be extremely difficult to get an A. I just need reassurance it's not going to be like 90 out of 100 to get an A then hopefully I can relax and enjoy my summer.
19. (Original post by Anna Louise)
I know a lot of people have been comparing this paper to the one in june 2011 but to anyone who's done the january 2012 paper do you think that paper was easier, harder, or about the same level as the one we've just sat ? Because a lot of people at my college were saying the one we've just sat was a better/easier paper (we did the january 2012 one as a mock) and I know for the paper last january the grade boundary was the highest it's ever been at about 83 out of 100 for an A. So now I'm worried that if people generally thought this paper was around the same level/easier it could be extremely difficult to get an A. I just need reassurance it's not going to be like 90 out of 100 to get an A then hopefully I can relax and enjoy my summer.
It is NOT going to be as high as 83/100 this time. The January paper was a lot easier (I did both). Couple that with most of the students taking the January paper being resitters (confirmed in the examiners report) high boundaries were imminent.
20. (Original post by myyrh)
It is NOT going to be as high as 83/100 this time. The January paper was a lot easier (I did both). Couple that with most of the students taking the January paper being resitters (confirmed in the examiners report) high boundaries were imminent.
Okay thank you Feel a lot more confident now ! Soo glad to hear that because thinking back to it I do think there was some harder question on this june paper which I had to really think about, specifically the one where the mechanism was outlined and you had to answer specific questions on it (Can't quite remember the exact question, sorry !) and also there weren't really any definitions apart from the 'curly arrow' one which I really was shocked to see on there. Anyways,I'm glad to hear you say this one was harder and that it definitely won't be 83 or higher for an A, think I was getting a bit a carried away :P And yes that's a really good point ! Well thank you, you've put my mind at rest Hope you get the grade you're hoping for and you have a good summer !

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Updated: December 11, 2012
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