Turn on thread page Beta
    Offline

    2
    ReputationRep:
    (Original post by student777)
    I wouldn't say they weren't worth practising... I found the UC papers particularly helpful because I tend to make stupid mistakes in calculations. So I would say if you need help on specific topics then you should do the old spec papers. However if you want an idea of the question styles etc then they're not going to be too helpful.
    So how shall we practise? Just the June'10 and Jan'11 paper? :eek: why does this always happen with us?!
    Offline

    0
    ReputationRep:
    On the Janurary 2011 exam, could someone explain part of question 7?

    It's the one about Dissolved Oxygen Concentration and working it out?

    The moles of S2O3^2- are 2.46x10^-5

    This is divided by 4 to find the the amount of O2.

    Where does the number 4 come from?

    Cheers
    Offline

    0
    ReputationRep:
    (Original post by 93M)
    On the Janurary 2011 exam, could someone explain part of question 7?

    It's the one about Dissolved Oxygen Concentration and working it out?

    The moles of S2O3^2- are 2.46x10^-5

    This is divided by 4 to find the the amount of O2.

    Where does the number 4 come from?

    Cheers
    This confused me as well. I thought you'd divide it by 2 instead of 4
    Offline

    15
    ReputationRep:
    Off to have spend an hour or so going over my answers and mistakes to 2010 june and 2011 jan :sigh:. Also going to do the specimen paper today, will probably return in tears :lol:.
    Offline

    1
    ReputationRep:
    (Original post by 93M)
    On the Janurary 2011 exam, could someone explain part of question 7?

    It's the one about Dissolved Oxygen Concentration and working it out?

    The moles of S2O3^2- are 2.46x10^-5

    This is divided by 4 to find the the amount of O2.

    Where does the number 4 come from?

    Cheers
    if you look at the equations 2 moles of S2O3 2- is equal to 2 moles of I-
    2 moles of I- is equal to 2 moles of MnO3 2-
    4 moles of MnO32- is equal to 1 mol of O2, so you divide the number of moles by 4

    you don't have to double the number of moles from the 2nd reaction to the 1st reaction because there is the same actual amount of moles there, its just they've redone the equation to balance it. but O2 is still a quarter of the moles of MnO3 2-

    its hard to explain, hope you understand haha
    Offline

    1
    ReputationRep:
    Midway through transition metals on my first run through on everything
    Offline

    1
    ReputationRep:
    On page 185 of the textbook
    at the bottom
    it says

    Fe2+ (aq) + e- ---> Fe3+ (aq)

    I know I have revision overkill and have lost the ability to grasp anything, but shouldn't that be the other way around? :confused:
    (think.I'm.going.mad)
    Offline

    15
    ReputationRep:
    (Original post by amyyy24)
    On page 185 of the textbook
    at the bottom
    it says

    Fe2+ (aq) + e- ---> Fe3+ (aq)

    I know I have revision overkill and have lost the ability to grasp anything, but shouldn't that be the other way around? :confused:
    [SIZE="1"](think.I'm.going.mad)[/SIZE]
    lol its a reversible reaction, and the electrons are always written on the left hand side in a half cell. The reaction will however go towards the left, therefore the other way around.

    Ok i understand i havent explained that very well, you might want to wait until someone else does .

    edit- Nope im wrong :facepalm: Chemistry has pushed me off the edge.
    Offline

    0
    ReputationRep:
    (Original post by amyyy24)
    On page 185 of the textbook
    at the bottom
    it says

    Fe2+ (aq) + e- ---> Fe3+ (aq)

    I know I have revision overkill and have lost the ability to grasp anything, but shouldn't that be the other way around? :confused:
    [SIZE="1"](think.I'm.going.mad)[/SIZE]
    yeah it should be Soo bad on behalf of the book!
    Offline

    1
    ReputationRep:
    Do we need to know how to name complexes? Because I was taught it, have forgotten it and i can't find it in the book...
    Offline

    0
    ReputationRep:
    (Original post by jontylol)
    Do we need to know how to name complexes? Because I was taught it, have forgotten it and i can't find it in the book...
    We were taught too but you don't need to know it for the exam. It's just background knowledge which may help/put you at ease in the exam
    Offline

    1
    ReputationRep:
    (Original post by sportycricketer)
    yeah it should be Soo bad on behalf of the book!
    I thought so, thanks

    (Original post by blush.ox)
    Chemistry has pushed me off the edge.
    I know the feeling!
    Offline

    8
    ReputationRep:
    (Original post by Rosi M)
    Ooo you probably have the same psychology exam as me.. PSYA4? Lets not even talk about that! :eek:

    I love benzene too but dont think it loves me back one bit!!!!
    :no: I'm edexcel. :sigh: I have done one bit of psychology...
    Cannot wait until this monster of a paper is finished. Then I can concentrate on psych/bio and more chem haha...
    Hopefully benzene loves us enough to come up on our paper
    Offline

    15
    ReputationRep:
    (Original post by INeedToRevise)
    Another thing to go over
    Hows revision going?
    I really hope we get an easy paper, born haber cycles and no redox titrations :ahhhhh: haha
    I like the maths best in this paper so would quite like some redox titrations. Plus i Like low grade boundaries.
    Offline

    0
    ReputationRep:
    YOu know for redox titrations, the sylabus states that carry out structured calculations involving I2 and S2O3(2-) and MnO4(-). Do we have to learn the equations for these titrations off by heart, or will they at least supply us with the relevant half equations???
    Offline

    0
    ReputationRep:
    Does anyone know the grade boundaries for the Jan 2011 paper?
    Offline

    8
    ReputationRep:
    (Original post by tallysingh)
    YOu know for redox titrations, the sylabus states that carry out structured calculations involving I2 and S2O3(2-) and MnO4(-). Do we have to learn the equations for these titrations off by heart, or will they at least supply us with the relevant half equations???
    I've been told to learn the equations!
    Offline

    0
    ReputationRep:
    do you think we will need to know the colour of transition metals in different oxidation states?
    Offline

    0
    ReputationRep:
    (Original post by entertheOJI)
    Does anyone know the grade boundaries for the Jan 2011 paper?
    it was 65/100 for an A.......and i got 60

    just type in OCR grade boundaries jan 2011 into google and it is the first link
    Offline

    8
    ReputationRep:
    I'm probably being dumb here, but why does K+ have a larger ionic radius than Ca2+. They would have the same number of electrons wouldn't they? 18...
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: December 10, 2012

University open days

  1. University of Bradford
    University-wide Postgraduate
    Wed, 25 Jul '18
  2. University of Buckingham
    Psychology Taster Tutorial Undergraduate
    Wed, 25 Jul '18
  3. Bournemouth University
    Clearing Campus Visit Undergraduate
    Wed, 1 Aug '18
Poll
How are you feeling in the run-up to Results Day 2018?

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.