Hey there! Sign in to join this conversationNew here? Join for free
    • Thread Starter
    Offline

    0
    ReputationRep:
    http://filestore.aqa.org.uk/subjects...5-QP-JAN12.PDF

    could somone pls help me understand the equation in q8 part ii about the complex standing in air ????? thanks !!!
    Offline

    3
    ReputationRep:
    (Original post by HG1)
    http://filestore.aqa.org.uk/subjects...5-QP-JAN12.PDF

    could somone pls help me understand the equation in q8 part ii about the complex standing in air ????? thanks !!!

    Have you looked at the mark scheme? What don't you understand?
    • Thread Starter
    Offline

    0
    ReputationRep:
    (Original post by TeachChemistry)
    Have you looked at the mark scheme? What don't you understand?

    yeah the mark scheme gives this 4(NH2CH2CH2NH2)3 (2+) + O2 + 2H2O GIVES 4(NH2CH2H2NH2)3 (3+) + 4OH-

    I just dont understand how you go about constructing the equation ?
    Offline

    3
    ReputationRep:
    (Original post by HG1)
    yeah the mark scheme gives this 4(NH2CH2CH2NH2)3 (2+) + O2 + 2H2O GIVES 4(NH2CH2H2NH2)3 (3+) + 4OH-

    I just dont understand how you go about constructing the equation ?

    You've missed the cobalt off but no matter.

    Write a half equation for cobalt oxidation from 2 to 3

    Write a half equation for oxiygen reduction to hydroxide.

    Balance electrons and combine half equations.

    The ligands on the cobalt do not change.
    • Thread Starter
    Offline

    0
    ReputationRep:
    (Original post by TeachChemistry)
    You've missed the cobalt off but no matter.

    Write a half equation for cobalt oxidation from 2 to 3

    Write a half equation for oxiygen reduction to hydroxide.

    Balance electrons and combine half equations.

    The ligands on the cobalt do not change.

    thanks alot ! really helped
    • Thread Starter
    Offline

    0
    ReputationRep:
    (Original post by TeachChemistry)
    You've missed the cobalt off but no matter.

    Write a half equation for cobalt oxidation from 2 to 3

    Write a half equation for oxiygen reduction to hydroxide.

    Balance electrons and combine half equations.

    The ligands on the cobalt do not change.
    This is how far I get , not sure where I went wrong ? And how do you know that oxygen is reduced to hydroxide ?
    Attached Images
     
    Offline

    3
    ReputationRep:
    (Original post by HG1)
    This is how far I get , not sure where I went wrong ? And how do you know that oxygen is reduced to hydroxide ?
    Your first equation is correct.

    The second is not correct. You can't have H+ and OH- in the same equation like that.

    Try this:

    2H2O + O2 + 4e- --> 4OH-

    now you finish off
 
 
 
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • Poll
    Would you like to hibernate through the winter months?
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • 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

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