OCR B Salters - F335 Exam - 15 June 2011

Mine was about 56 Pages, and I don't think I've worked so hard or worried so much in my life. I was so relieved that I'd done well in it though, as well it would have added more stress to this exam otherwise.

iknow right !! my project lasted like 2 months and all together my report was like 20,000 words (because i did enzyme reaction so i had to test every factor that affects the rate of reaction) it felt like i was in Uni coz the teachers weren't allowed to help us looool

I plan on doing English literature and like a complete moron took chemistry into A level. This is completely going to stop me going to my firm...it's so depressing

Too true, it was boring on for so long that it got tiresome!! Ahh I did the hydrogen peroxide one, inorganic and organic catalytic decomposition. Goood times! I actually found the project a good time for getting to know class mates even better, spending like 18 hours with them..

I did that one! :] What mark did you end up getting?
I had real trouble trying to get the concentration of the hydrogen peroxide... Everyone was stumped :'D got there in the end though

It's the best one! There was my friends with their burettes and titrating, I'm just chilling with the Buchner flasks Might of broken one though. Oops! :P
I got 80/90 in the end, was well happy with that, how'd you do?
Ahhh well we have this little "recipe" book for making up different concentrations of hydrogen peroxide in terms of volume, like 10 vol etc

Haha! :P
Ours was given to us at '20vols' and you had to titrate it against known potassium permanganate that you made yourself
I sat and just read off the inverted burette :'D
It all looked very professional, wearing a lab coat, goggles and stood watching with a clipboard :'D
Well done you!
I only got 74... It's an A though so it's okay
What catalysts did you use?

Ahhh I see, well our technicians made something like 10 vol up but we had to make some up ourselves
Yeah that's what we thought! We was all there looking like pro's :P
Thanks That's good though, getting an A is something to be proud of :
Errrrm I think for inorganic I used Manganese Dioxide and Lead oxide, and for organic just a catalase enzyme using yeast suspension. How about you?

People walk in the room and treat you with respect... Because you're a chemist ;]
We ran out of HP towards the end so I bottled some up and kept it in the corner with me :'D whoops
I used Lead (II) oxide, Lead (IV) oxide and Manganese (IV) oxide... The first time I used the manganese I didn't realise how... Rapid... A catalyst it was :'D
So, just put 1g into 25cm3 of hydrogen peroxide...
It shot out and I dropped it then had to clean up the mess :'D haha :'D
I didn't have time to do the yeast one... I spent over 27 hours in there :'D

I know right, chemists are awesome..
HP thief!! :P We had loaaads of HP!
Ahhh I only used Lead (IV) and Manganese (IV), I dunno why but the Lead one was really fast I think D:
Lmaooo that sounds like a lot of fun.. :P You must of been using more conc HP that me because that didn't happen with me :O
Wow! That's a lot of time :L Doing the yeast one is awesome because the room smells like alcohol when you're aerating it...

I ended up producing ridiculous amounts of Bromine gas which started a bit of a coughing fit at one point in my experiment. I couldn't get the smell away either, it took about a week to go away. Of course, this was never mentioned in the write up :P

Hahaha :'D that's brilliant :'D
I wasn't drunk on fumes during my chemistry investigation ;]
Agreed, Lead was quite fast as well... The manganese went on my friends coat as well... Not much... But I was just like 'please don't notice!' I don't think she did... :'D
Did you get any hydrogen peroxide on your hands?
I did on the first day and when my hands were bright white, it freaked me out a bit because I thought it would never go away :'D

Yeah maybe just a little tipsy from the yeast fumes
Haha! Hope she didn't notice! :P Just hope she doesn't get some HP on her in some weird coincidence and it starts fizzing :P
Errrrm I can't recall getting any on me no, sounds sore though.. :P
What/where have you applied for then?

Did you come out with noticeably whiter teeth? (Hydrogen Peroxide is used in teeth whitening)

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

Is there any chance you can do this for question 4 and 5? I need to find out how I've done to decide whether to retake f334... would be much appreciated

Yeah i will do now

can i ask yah, what would be the conjugate acid of H2Po4- ??