Hey there! Sign in to join this conversationNew here? Join for free
x Turn on thread page Beta
    Offline

    8
    ReputationRep:
    (Original post by ravichauhan11)
    everyone remember to include that deltaH was approx 0 because same amount and type of bonds being broken and formed? for the thermo stability Q
    Yup I put this down.


    Posted from TSR Mobile
    Offline

    2
    ReputationRep:
    (Original post by cowie)
    I drew two lines and wrote a caption for each..
    One was horizontal and I mentioned fuel was constantly sullied
    The other was a curve with decreasing gradient and I mentioned this was when fuel was not constantly suplied


    Posted from TSR Mobile
    You can't draw two lines can you?
    Offline

    8
    ReputationRep:
    (Original post by Whitney997)
    What equations did you guys write for each electrode in the hydrogen-oxygen fuel cell question?
    +ve electrode: O2 + 4e + 2H+ = 2OH-
    -ve electrode: H2 + 2OH- = 2H2O + 4e
    full equation: H2 + 02 + 2H+ = 2H2O
    I'm pretty sure this is wrong though
    What did everyone else get?
    Offline

    0
    ReputationRep:
    (Original post by crillieswillies)
    Any idea how many marks I'd lose for getting delta G as -135000? I multiplied delta H by 1000 so delta H and delta S were in the same units :'(
    - 135000 is right as long as you wrote J mol^-1 as units
    Offline

    2
    ReputationRep:
    (Original post by ravichauhan11)
    everyone remember to include that deltaH was approx 0 because same amount and type of bonds being broken and formed? for the thermo stability Q
    No - the starting reactant was [Co(H2O)6]2+ and the product was [Co(h2nch2ch2nh2)3]2+ not same type of bonds are broken as are formed but same number yes


    Posted from TSR Mobile
    Offline

    1
    ReputationRep:
    What did everyone get for the characteristics of chromium chemistry question?
    Offline

    2
    ReputationRep:
    I sat last years paper and this year's and I think they're about the same in difficulty although the calculation on this year's may have tripped up more people so I think the grade boundaries will be about the same if not one ums less for each grade boundary compared to last year
    Offline

    2
    (Original post by Cadherin)
    5/7 with ALL correct working shown.
    -A1 for correct answer
    -M4 for dividing by 3
    Did you say catalyst for last quesiton was Mn2+ and tick H2SO4?
    Offline

    2
    ReputationRep:
    (Original post by Pippy12345)
    What did everyone get for the characteristics of chromium chemistry question?
    Coloured complexes
    Variable oxidation states
    Compex ions
    And i gave examples for each :/


    Posted from TSR Mobile
    Offline

    2
    ReputationRep:
    (Original post by 12284)
    +ve electrode: O2 + 4e + 2H+ = 2OH-
    -ve electrode: H2 + 2OH- = 2H2O + 4e
    full equation: H2 + 02 + 2H+ = 2H2O
    I'm pretty sure this is wrong though
    What did everyone else get?
    +ve was O2 + 2 H20 + 4e -> 4OH-

    The conditions were in alkaline so you can't have H+ ions in your equation.
    Offline

    0
    ReputationRep:
    (Original post by BigWillow)
    You lose none thats correct
    Phew! Thank you.
    Offline

    2
    ReputationRep:
    (Original post by Suits101)
    Did you say catalyst for last quesiton was Mn2+ and tick H2SO4?
    I had Mn2+ and H2SO4
    Offline

    1
    ReputationRep:
    (Original post by randoms132)
    Coloured complexes
    Variable oxidation states
    Compex ions
    And i gave examples for each :/


    Posted from TSR Mobile
    Did it ask for examples?
    Offline

    1
    ReputationRep:
    (Original post by crillieswillies)
    Any idea how many marks I'd lose for getting delta G as -135000? I multiplied delta H by 1000 so delta H and delta S were in the same units :'(
    Did you write the units of deltaG as Jmol-1? If you did then you should get all the marks I think!

    Then if you did deltaS divided by 1000 instead you'd have to give units of deltaG to be kJmol-1 right?
    Offline

    2
    ReputationRep:
    (Original post by RME11)
    +ve was O2 + 2 H20 + 4e -> 4OH-

    The conditions were in alkaline so you can't have H+ ions in your equation.
    I got the equation but .5o2 + h20 + 2e- -> 2oh- still acceptable?
    Offline

    2
    (Original post by ravichauhan11)
    everyone remember to include that deltaH was approx 0 because same amount and type of bonds being broken and formed? for the thermo stability Q
    Yup

    And Delta G <= 0
    Offline

    2
    ReputationRep:
    (Original post by Pippy12345)
    Did it ask for examples?
    No it didnt :-)


    Posted from TSR Mobile
    Offline

    8
    ReputationRep:
    (Original post by Suits101)
    For redox questions:

    Weakest OA: Zn2+
    Conventional cell diagram: Zn | Zn2+ || Co2+ | Co
    Half equation: Zn -> Zn2+ + 2e-
    Cobalt species: Co3+, oxidation product is oxygen, then reaction

    Negative electrode: H2 + 2OH- -> 2H2O + 2e-
    Positive electrode: 4e- + O2 + 2H2O -> 4OH-
    Overall reaction: 2H2 + O2 -> 2H2O
    Graph of emf: just a straight horizontal line
    Isn't the positive and negative electrodes the wrong way around?
    Offline

    2
    ReputationRep:
    (Original post by randoms132)
    No - the starting reactant was [Co(H2O)6]2+ and the product was [Co(h2nch2ch2nh2)3]2+ not same type of bonds are broken as are formed but same number yes


    Posted from TSR Mobile
    same question came up in 2014, mark scheme : " Allow same number and type of bonds broken andformed"
    Offline

    2
    ReputationRep:
    (Original post by Pippy12345)
    Did it ask for examples?
    No, just said state 3 characteristics
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: August 27, 2016
Poll
Do you agree with the proposed ban on plastic straws and cotton buds?

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.