OCR F324-June 2013 Chemistry

Original post by Zzzyax

Hi
Perhaps someone can help me with this question: how many electrons are involved in the pi bonding in benzene, between 2 adjacent carbons, and explain what each of the valency electrons in a carbon atom do (what type of bond sigma pi etc, what bonded with) in benzene.

Any help appreciated, (and plus rep for you also)

Right. Each Carbon atom has 4 valency electrons. In Benzene, each Carbon atom has 3 sigma bonds - one with each of the adjacent Carbon atoms, and one with the Hydrogen atom. The remaining valency electron is in a p-orbital. The p-orbitals of the remaining valency electrons of all the Carbon atoms in Benzene overlap, forming pi bonds over the whole structure - this gives a region of high electron density above and below the ring. This means one electron from each Carbon, or 6 electrons altogether, are involved in the pi-bonds in Benzene.

Reply 1022

Zzzyax

Original post by Zaphod77

Right. Each Carbon atom has 4 valency electrons. In Benzene, each Carbon atom has 3 sigma bonds - one with each of the adjacent Carbon atoms, and one with the Hydrogen atom. The remaining valency electron is in a p-orbital. The p-orbitals of the remaining valency electrons of all the Carbon atoms in Benzene overlap, forming pi bonds over the whole structure - this gives a region of high electron density above and below the ring. This means one electron from each Carbon, or 6 electrons altogether, are involved in the pi-bonds in Benzene.

thanks alot, you cleared everything up for me

Reply 1023

Original post by Zzzyax

thanks alot, you cleared everything up for me

Good! No problem :smile:

Reply 1024

Anyone know what the stretch and challenge boxes are for in the book?

Reply 1025

printergirl

13

Original post by master y

Anyone know what the stretch and challenge boxes are for in the book?

Exactly what is says :tongue:

Its not needed for the exam, just there to make you think

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Reply 1026

Lilmzbest

Original post by master y

Anyone know what the stretch and challenge boxes are for in the book?

Its not on the spec so won't really be tested on, but I do physics OCR and apparently they once tested on something from the stretch and challenge boxes ... so i read it just in case :colondollar:

Edit: why the neg rep :confused:

(edited 10 years ago)

Reply 1027

Original post by Lilmzbest

Its not on the spec so won't really be tested on, but I do physics OCR and apparently they once tested on something from the stretch and challenge boxes ... so i read it just in case :colondollar:

Edit: why the neg rep :confused:

What OCR sometimes do is put in a question that relates to a stretch and challenge box, as normally the stretch-and-challenge is just putting some fact in context. This means exam questions can be linked to stretch-and-challenge, but you don't have to learn all the content in them necessarily, they'll give you the factual side, it's just learning to apply knowledge you've learned!

Reply 1028

Just wondering if anyone has done a qualitative on redox and precipitation, and if so what is the actual title/what can ocr tell u about it? Thanks

Reply 1029

Zzzyax

i hate chemistry, i got my final coursework mark today 33/40 isnt even an A, even though i got 144/150 in jan F325, i will be very difficult to me to get an A*, our teacher gives us **** all help with the coursework unlike some others teachers in different schools, she just tells use vague areas to revise.coursework is unfair and flawed. how the **** can someone get a really high mark in in F325 and a B in coursework. anyone any advice of how i can justify to the examiner to award me an a star.

Reply 1030

Original post by Zzzyax

i hate chemistry, i got my final coursework mark today 33/40 isnt even an A, even though i got 144/150 in jan F325, i will be very difficult to me to get an A*, our teacher gives us **** all help with the coursework unlike some others teachers in different schools, she just tells use vague areas to revise.coursework is unfair and flawed. how the **** can someone get a really high mark in in F325 and a B in coursework. anyone any advice of how i can justify to the examiner to award me an a star.

33/40 on coursework will correspond to 41 UMS, if my calculations are correct. Because you did so well in F325, you have bang on a 90% average between F325 and coursework. This means you need 81/90 UMS in the small exam - you got 144/150 in the big exam, it's perfectly possible! Don't give up hope, just work hard, you can get there :smile:

Reply 1031

Lilmzbest

Hi guys, i have a qualitative coursework on investigating chemical reactions of some chromium compounds and then we have to identify two organic compounds, has anyone else done this? i don't know what i'm supposed to be revising :confused:

Reply 1032

betbea20

Original post by physicshelp123

anyone got any tips for the determination of a formula practical???

I'm doing this on friday! Anyone got any tips? We've basically been told nothing and I'm really worried. This is the evaluative if I'm not mistaken

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Reply 1033

Hey everyone, haha this has basically become a practical thread, so i was wondering if anyone has done a quantitative on free energy, and if so do they have any tips?

Reply 1034

Original post by kimsiclez

Nope, but I have an evaluative coming up on Electrode Potentials and a Quantitative the next day on Free Energy. Neither of which topics I fully understand (our teacher is rubbish). Wahey.

Has anyone else's school left literally all the practicals until now? I mean, we've done a grand total of two so far. It's annoying that most of them seem to be related to topics towards the end of the syllabus. :angry:

Hey, i was just wondering how the practical in free energy went, do you have any tips? Thank you, i would appreciate your help! I am pretty much like this atm --> :bricks:

Reply 1035

Zzzyax

Original post by master y

Hey, i was just wondering how the practical in free energy went, do you have any tips? Thank you, i would appreciate your help! I am pretty much like this atm --> :bricks:

Has anyone done evaluative on electrode potentials?
i have recently done qualitative on chromium and a something on free energy change of formation, pm me :smile:

Reply 1036

otrivine

OP

14

Original post by Zzzyax

Has anyone done evaluative on electrode potentials?
i have recently done qualitative on chromium and a something on free energy change of formation, pm me :smile:

Hi want to revise :smile:

Reply 1037

dwindledStrangly

7

Hi,

I recently printed out a copy of the huge F324 questions pack, but the answers copy had a block on it co it could be printed. I would be helpful if anyone could post a copy of the answers that i can print, i really want to start revising. :cool:

The link of my questions pack: https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CDUQFjAB&url=http%3A%2F%2Fwww.thestudentroom.co.uk%2Fattachment.php%3Fattachmentid%3D95681%26d%3D..&ei=hk2CUcSMDuiU0QXe44HICw&usg=AFQjCNEvKOp9BA2DP3mFEUD-q0BoqHU8cQ&bvm=bv.45921128,d.d2k
The link that wouldn't let me print: https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CDMQFjAA&url=http%3A%2F%2Fwww.thestudentroom.co.uk%2Fattachment.php%3Fattachmentid%3D95682%26d%3D1295516178&ei=hk2CUcSMDuiU0QXe44HICw&usg=AFQjCNFhEyeng9AOgBu94DPh1Kgvqs_8-A&bvm=bv.45921128,d.d2k

Reply 1038

otrivine

OP

14

Original post by master y

For an A you need 60/90 ums, and i think you can't get an A*...

Hi want to revise

Reply 1039

Blue_Birdie