Turn on thread page Beta
    Offline

    0
    ReputationRep:
    (Original post by apo1324)
    Has the mark scheme for the jan 2011 paper been posted by any chance? :P
    yes, check the first page of this thread
    Offline

    8
    ReputationRep:
    People, how do you rearrange a born haber cycle to find something other than lattice enthalpy? just had a mind block and the book doesn't make sense to me..
    Offline

    0
    ReputationRep:
    just did the 2011 jan paper and got 78 but the only reason i am happy is BECAUSE I FINALLY KNOW HOW TO DO REDOX EQUATIONS
    HIP HIP HURAY!!!!

    i am however gonna "ignore" any questions on enthalpy of solution/hydration .... dont get it!

    good luck everyone!!
    lool imagine if we get another hair perm style question. haha fingers crossed its a lovely paper!!!!!
    Offline

    2
    ReputationRep:
    (Original post by goldlock)
    The rate equation gives you the reactants and the molar quantities (look at the power of each reactant concentrations) involved in one step (the rate - determining step) of the reaction. I don't think there's any specific rule that it has to be the first step but I think it's decent practice to put it down as the first.
    Okay. But is it like the product/s of the 1st step are the reactants in the second step which react to form the overall product of the reaction? I'm confused
    Offline

    0
    ReputationRep:
    (Original post by entertheOJI)
    [[Fe(H20)6]2+] over [Fe2+]

    sorry, I don't know why I included H20 the first time. sorry for any confusion caused.
    Would you not include the H20 because it's a reactant? I thought you would only disregard it if it is generated as a product as it is in great excess anyway.
    Offline

    0
    ReputationRep:
    1) buffer systems --- HOW TO REMEMBER AND ANSWER TO GET MAXIMUM MARKS ?

    2) IN MANUFACTURE OF CaC2 what is the maximum mass of CaC2 that can be obtained from 40.0kg of Ca0 and 4kg of CO?

    CaO+ 3C------> CaC2 + CO
    Offline

    1
    ReputationRep:
    (Original post by 786girl)
    just did the 2011 jan paper and got 78 but the only reason i am happy is BECAUSE I FINALLY KNOW HOW TO DO REDOX EQUATIONS
    HIP HIP HURAY!!!!

    i am however gonna "ignore" any questions on enthalpy of solution/hydration .... dont get it!

    good luck everyone!!
    lool imagine if we get another hair perm style question. haha fingers crossed its a lovely paper!!!!!
    I'm on question 5 c) at the moment about carrying out the experiment etcetc
    The hairspray question blew my mind not a clue on that!!
    Offline

    0
    ReputationRep:
    (Original post by Student21)
    Okay. But is it like the product/s of the 1st step are the reactants in the second step which react to form the overall product of the reaction? I'm confused
    No denying this topic's a bit awkward - you need to write out the reactants of the first step from the rate equation, then below that, leave space for the second step and write the overall equation - you have to do a bit of detective work to fit that stuff together, the products of step 1 aren't always the reactants for step 2
    Offline

    0
    ReputationRep:
    (Original post by goldlock)
    I'd begin by writing down all of the reactants/products that you're given in the question, aside from any hydroxide ions, protons or H20 that you may well need to even things up - so, begin with saying that N02 + I- goes to I2 + NO
    Then, you need to work out which of these atoms change oxidation number, and balance those atmos that do (so, I goes from -1 to 0 so balance the number of iodines). That should set you on your way
    so would the answer be ...:

    H20 +I2 + NO2 - -----> NO + 2I- + 2OH-
    Offline

    0
    ReputationRep:
    Going to fail this badly :/
    Offline

    0
    ReputationRep:
    (Original post by bambinooo)
    so would the answer be ...:

    H20 +I2 + NO2 - -----> NO + 2I- + 2OH-
    Afraid not the atoms balance but the charges don't - look more closely at how N changes its oxidation number
    Offline

    0
    ReputationRep:
    any main things to keep in mind on buffer questions?
    Offline

    2
    ReputationRep:
    Could somone explain to me 4bii in the jan 2011 paper please. :L
    Offline

    0
    ReputationRep:
    (Original post by grainyshadeofgrey)
    any main things to keep in mind on buffer questions?
    I reckon a question'll come up that asks for the pH of a buffer, the main thing to bear in mind being that the concentration of the base doesn't equal the conc. of H+, the carbonic acid hydrogencarbonate stuff too, that'll probably show.
    Offline

    2
    ReputationRep:
    (Original post by susan23)
    exo is making bonds -Ve
    endo is breaking bonds +Ve

    ex-girlfriend makes *****es negative
    enormous butt is breaking positive

    LOL thats soooo crap....ahhahahahahaah
    so sorry about that they dont even make sense
    Hahahah
    Its difficult to remember your codes!

    I remember one in BIo
    King philip came over for great sex!


    Just realised this is the last paper and perhaps synoptic but havent seen any synoptic question so far!!!!!!:eek:
    Offline

    0
    ReputationRep:
    (Original post by grainyshadeofgrey)
    any main things to keep in mind on buffer questions?
    - Made from weak acid and salt of a weak acid.

    - Uses equilibrium (HA ---> H^+ + A^-) to minimise pH changes

    - When H^+ is added to the buffer solution it reacts with the conjugate base A^- and the position of equilibrium shifts to the left removing the added H^+ ions.

    - When OH^- is added to the buffer solution it reacts with a small concentration of H^+ ions (H^+ + OH^- ---> H2O). HA (weak acid) dissociates and the equilibrium shifts to the right restoring the H^+ ions that reacted.

    ^ That's the most important stuff.
    Offline

    0
    ReputationRep:
    (Original post by goldlock)
    afraid not the atoms balance but the charges don't - look more closely at how n changes its oxidation number
    does n go from 3+ to 2+??
    Offline

    0
    ReputationRep:
    (Original post by bambinooo)
    does n go from 3+ to 2+??
    It does, so you can use that to think about the overall change in oxidation/reduction
    Offline

    0
    ReputationRep:
    (Original post by hiyarearl)
    - made from weak acid and salt of a weak acid.

    - uses equilibrium (ha ---> h^+ + a^-) to minimise ph changes

    - when h^+ is added to the buffer solution it reacts with the conjugate base a^- and the position of equilibrium shifts to the left removing the added h^+ ions.

    - when oh^- is added to the buffer solution it reacts with a small concentration of h^+ ions (h^+ + oh^- ---> h2o). Ha (weak acid) dissociates and the equilibrium shifts to the right restoring the h^+ ions that reacted.

    ^ that's the most important stuff.
    thank you
    Offline

    0
    ReputationRep:
    I feel like crying. I just got 55 out of 100 on the June 2010 paper! Can someone please tell me what grade it is according to the grade boundaries for this paper? I can't find it anywhere! Please quote me! Thanks!
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: December 10, 2012
Poll
Do you think parents should charge rent?

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.