OCR B Salters - F335 Exam - 15 June 2011

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Looking back at some of the answers, it seems people put varying answers for the SF6 question; therefore, a quick question...
I put the latter (SF6 Possible structure/picture on the right without the bond angles) in my exam, when the correct answer was the one on the left/(bond angles).

Aren't they the same? or would the examiners be wanting the one on the left? :confused:

Thanks in advance. :smile:

Yes thats how i drew it. It is the same if you think about it but you know how examiners can be strict.

Reply 961

littlesparrow

Original post by 41jms

This annoyed me slightly :tongue:

Regardless of what my views are on the difficulty of that paper i disagree completely with what you've said because ofcourse grade boundaries do vary for each year/paper. Just because you thought it was the same/easier than the last 2 papers doesnt mean much really (just like my opinion doesnt mean much) as it is simply one single person's views. Generally, from my quite large year group and people on this thread the impression is that the paper was difficult in comparison to the previous papers - nobody is saying every single aspect of it was hard, there definitely were some "gift" questions (electrophile definition, colour, pH etc) but on the whole i think it is fair to say most people found it challenging. Youve got to be aware of the fact that you have taken this paper for a third time, ofcourse it will seem easier to you - it doesnt matter if you have done less revision or whatever, just the fact that you've been familiar with F335 for over a year is enough to make you more prepared/experienced/aware of this exam.

just saying. :smile:

Well said bruv, +rep

Reply 962

limetang

Original post by jpurkis1

Thanks in advance. :smile:

They're both the same shape. So examiners should accept either. I mean I did the one on the left more because that's the way I learnt to represent it, and although the one on the right isn't the typical way of representing it, it should be fine as it still represents the same shape.

(edited 12 years ago)

Reply 963

Daveedwards8

Any danger of a mark scheme?

Reply 964

hahahah

Original post by jpurkis1

Thanks in advance. :smile:

i drew both of these in the exam! then i crossed out the right one, i think they would want the left one!

Reply 965

zahre

I was just wondering if we were to go by Januarys grade boundaries which was 80 raw marks out of 120 for an A (96 ums) how many raw marks would you approximately need to get a ums mark of say 105? does anybody know? :smile:

Reply 966

goodezy12

Original post by zahre

It goes in 9 marks for 12 ums.. so 89 marks would get you 108 ums.. so 105 would probably be about 87raw marks. But the mark scheme before (june 2010) was 85 for an A- so about 92 raw marks.
This is just guessing to be honest, but seems right¬!

Reply 967

libbymimnagh

Original post by laurenl93

So I'm guessing noone else noticed that the NMR spectrum of TE bromine molecule was wrong?

One of the peaks corresponded to a proton attached to an alkene environment, my entire year noticed it & the head of chemistry?

Bitch of a paper though, at one point k was physically shaking so much I couldn't write... & imagining my life as a binman :tongue:

I noticed it! So did several others!
I'm writing an email to OCR right now complaining about that mistake and the mistake in another paper I sat this morning.
Absolute joke... These people need to hire decent proof readers :angry:

Reply 968

zahre

Original post by goodezy12

It goes in 9 marks for 12 ums.. so 89 marks would get you 108 ums.. so 105 would probably be about 87raw marks. But the mark scheme before (june 2010) was 85 for an A- so about 92 raw marks. This is just guessing to be honest, but seems right¬!

Thanks alot. In my opinion the paper we did on last wednesday was of equal difficulty if not more difficult than January so hoping grade boundaries are similar to Jan or maybe lower if lucky.

Reply 969

dan1993

Original post by libbymimnagh

there's no point complaining about that because at the bottom of the data sheet it says " the chemical shift is sensitive to temperature, nature of the solvent and concentration." So they will just point this out and in regards to your other exam there was an article on the bbc wesbite about more errors being found....did u do the ocr physics paper?

Reply 970

SmileyGurl13

Original post by libbymimnagh

I don't think it's a mistake :/ the exact chemical shifts depend on neighbouring environments and conditions, the range is a rough guideline and tbh it was pretty close. Plus you didn't even need it, it wasn't asking for shifts at all!

Reply 971

goodezy12

Original post by zahre

Thanks alot. In my opinion the paper we did on last wednesday was of equal difficulty if not more difficult than January so hoping grade boundaries are similar to Jan or maybe lower if lucky.

Personally I found it way harder yeah, as have other people on this forum... but then again people in my school found it okay, so we'll see. 73-4 for a B would do me nicely :smile:

Reply 972

Kartace

Originally Posted by ManPowa
Question 2

Oxidation and reduction (4 marks) Not sure!!!

Equation: sulfur tetrafluoride plus oxygen to form sulfur hexafluoride

Electron configuration: 1s2 2s2 2p6 3s2 3p4

Dot and cross for SF6: 6 groups of electrons around the central sulfur atom.. one electron from sulfur and one from fluorine. 3 lone pairs on each fluorine atom.

3D shape of Sf6 and a bond angle of 90 degrees.

Mass of lithium: 112 KG

Systematic name for Li2S: Lithium sulfide

Bonding:
Lithium - metallic
Sulfur trioxide - covalent
lithium fluoride : ionic

Explain why SF6 is a gas at room temperature while hexanedioic acid is a solid: Answer people/!!!

Entropy change of system (2)

Total entropy change (2)

Formula of potassium chlorate(VII) - I Put KCLO4 - the clorine has a an oxidation state of 7

Comment - If your total entropy was positive, then a fuse will not be required as the reaction is spontaneous. However, if your toral entropy change was negative, then a fuse will be required. I think on the mark scheme, this will be ECF as even if you get the wrong answer but you can still get the mark for the comment.

29 marks

I'll be honest, i disagree slightly with the answer to the splint question. I have a feeling that the answer may have been something to do with a large value for Ea. As you were supposed to realise that the etropy value could not have been the reason for the use of the splint.

I just dont think that it would be as simple an answer as, "the splint was not needed" Although there will doubtless be a mark to pick up somewhere for mentioning the effect of the Entropy value.

Reply 973

hbaker10

Maybe a splint as it was an explosive reaction so it was a safety precaution?

Reply 974

Nucleolus

I can't believe how many mistakes I made on that paper, hello U and goodbye medicine.

Reply 975

hbaker10

http://books.google.co.uk/books?id=0X4cQus2gz8C&pg=PA385&lpg=PA385&dq=1,1-dibromoethane+nmr+shift&source=bl&ots=64sLzmjAxJ&sig=jralix1yA3rD7dKUyysgV96k8kI&hl=en&ei=uPUATqb9J42t8QOmrICTDQ&sa=X&oi=book_result&ct=result&resnum=9&ved=0CFcQ6AEwCA#v=onepage&q=1%2C1-dibromoethane%20nmr%20shift&f=false

NMR q didn't have the wrong shifts either>

Reply 976

libbymimnagh

Original post by dan1993

Yes I did sit the Physics paper this morning.
And while you say that, the head of chem at my school came into the exam room and alerted us all the mistake which I had spent a good 10 minutes looking at beforehand... I thought I wasn't reading the spectrum properly! My eyesight isn't the best at times, I genuinely thought I was reading the axis incorrectly! Several others who sat the exam with me also came out saying that they had wasted a lot of time on that question.
Most of the past paper nmr questions I had done for this were a lot clearer than that particular one, that's all I'm saying.
I guess I'm just annoyed at OCR in general - I've sat 2 papers so far this summer, and both have contained a mistake to some degree that have caught me out and wasted my time :frown:

Reply 977

libbymimnagh

Original post by SmileyGurl13

I realise it wasn't asking for shifts, however I was just double checking them for myself during the exam - I wanted to ensure that the structure I had decided on was correct. When I started to look at it more closely, I got really confused and a bit panicky I must admit! I guess exam nerves just got to me...

Reply 978

SmileyGurl13

Original post by libbymimnagh

I know it may seem unfair and it's annoying that people (including myself) spent ages trying to figure it out it is correct and if you look at the link above it defo is! They would have got in trouble if they had given what we wanted to see because it isn't correct :/ so unfortunately there's nothing we can do! The paper was right.

Reply 979

dan1993

Original post by libbymimnagh

yeah i no how you feel....i did the ocr biology paper and i spent weeks revising it only to find that the exam was irrelevant and that i probably would have got the same mark if i hadn't of revised. OCR is messed up in general. But what i was trying to say is that there is nothing anyone can do about the nmr question as if u complain then they will just direct you to the data sheet. anyways good luck with the rest of your exams :smile: