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

    2
    ReputationRep:
    (Original post by Signorina)
    Yes ur correct in sense for the born haber cycle you would use -695 because you need two electron affinities

    However The question is "what's the electron affinity of chlorine?

    Think of it as:
    2 x electron affinity of Cl = -695

    You just want the electron affinity of Cl so

    Electron affinity of Cl = -695/2

    It's hard to explain and I understand why you're struggling to understand it but just remember the definition of electron affinity... The energy change when one mole of gaseous atoms gains one mole of electrons. What you found out is the energy change when TWO moles of gaseous atoms ......etc

    Hence why you need to divide by two.
    Thanks a lot your explanation has made it much clearer in my head
    Offline

    1
    ReputationRep:
    (Original post by ahsan_ijaz)
    Thanks a lot your explanation has made it much clearer in my head
    Is this exam for the old A Level spec??
    Offline

    20
    ReputationRep:
    (Original post by L1234567)
    Is this exam for the old A Level spec??
    Yes
    This is exam for the new a level spec hasn't even started


    Posted from TSR Mobile
    Offline

    1
    ReputationRep:
    (Original post by Bloom77)
    Yes
    This is exam for the new a level spec hasn't even started


    Posted from TSR Mobile
    Ohh, I just wanted to know whether they will still make papers for the new A Level papers.
    Offline

    2
    ReputationRep:
    can someone help me with this question 5b(i) to 5(b)iv its structure determination

    I got the answer right when asked to deduce the structure of P, BUT my structure was the other way around, (so the same as the mark scheme if read in the opposite direction) do you get penalised for this, as i didnt see anything that said you would in the additional comments. if you do, then can someone explain to me how you know which way to draw the structure. thank you!
    past paper question 5biv: http://filestore.aqa.org.uk/subjects...4-QP-JAN13.PDF
    mark scheme: http://filestore.aqa.org.uk/subjects...W-MS-JAN13.PDF
    Offline

    3
    ReputationRep:
    (Original post by chzm)
    can someone help me with this question 5b(i) to 5(b)iv its structure determination

    I got the answer right when asked to deduce the structure of P, BUT my structure was the other way around, (so the same as the mark scheme if read in the opposite direction) do you get penalised for this, as i didnt see anything that said you would in the additional comments. if you do, then can someone explain to me how you know which way to draw the structure. thank you!
    past paper question 5biv: http://filestore.aqa.org.uk/subjects...4-QP-JAN13.PDF
    mark scheme: http://filestore.aqa.org.uk/subjects...W-MS-JAN13.PDF
    I did that as well but i think there is no problem.
    Offline

    3
    ReputationRep:
    Hi all, can you please post the hardest questions in unit 4 or 5 that you have experienced. Also, please state the source it is from if possible.Thanks a lot.
    Offline

    2
    ReputationRep:
    For the polymers topic, what exactly do we have to specificically have to memorise/regurgitate re: Kevlar, Nylon and terylene.

    Do we need to know the monomers for each by heart? Or just how to form the polyester/polyamide once they give us the monomers or?

    Thanks
    Offline

    20
    ReputationRep:
    (Original post by hi-zen-berg)
    For the polymers topic, what exactly do we have to specificically have to memorise/regurgitate re: Kevlar, Nylon and terylene.

    Do we need to know the monomers for each by heart? Or just how to form the polyester/polyamide once they give us the monomers or?

    Thanks
    I understand you have to know the polymers by heart, but if you memorise the monomers, then you can make the polymers easily


    Posted from TSR Mobile
    Offline

    20
    ReputationRep:
    Hi
    I don't seem to understand the answer to this question
    Name:  ImageUploadedByStudent Room1464851560.777058.jpg
Views: 164
Size:  107.6 KB

    Answer:
    Name:  ImageUploadedByStudent Room1464851581.754970.jpg
Views: 137
Size:  115.6 KB


    Posted from TSR Mobile
    Offline

    3
    ReputationRep:
    (Original post by Bloom77)
    Hi
    I don't seem to understand the answer to this question



    Posted from TSR Mobile
    So enthalpy of solution is when the ionic compound is dissolved in enought water making sure the ions dont interact. When this happens, the equation will show 1 reactant producing 2 reactants. So the no. Of moles on RHS is higher than LHS. increase in moles=increase in entropy so the value of T¤S will always be bigger than H and so G will always be negative.
    Offline

    20
    ReputationRep:
    (Original post by theboss1998)
    So enthalpy of solution is when the ionic compound is dissolved in enought water making sure the ions dont interact. When this happens, the equation will show 1 reactant producing 2 reactants. So the no. Of moles on RHS is higher than LHS. increase in moles=increase in entropy so the value of T¤S will always be bigger than H and so G will always be negative.
    OMFG YOUR A STAR!
    Thank you!


    Posted from TSR Mobile
    Offline

    3
    ReputationRep:
    (Original post by Bloom77)
    OMFG YOUR A STAR!
    Thank you!


    Posted from TSR Mobile
    No problem. Happy to help!

    Any body else who has a question either post it here or PM me and I will explain it.
    Offline

    8
    ReputationRep:
    I was wondering if someone could explain 8ei for me? I answered it so that it acted as a ligand on Aluminium but in the mark scheme it acts as a base- how can you distinguish whether it will act as a ligand or a base?
    Attached Images
      
    Offline

    3
    ReputationRep:
    (Original post by youngar)
    I was wondering if someone could explain 8ei for me? I answered it so that it acted as a ligand on Aluminium but in the mark scheme it acts as a base- how can you distinguish whether it will act as a ligand or a base?
    Ok so as a ligand you get full substitution. As a base the diaminoethane acts as brownsted-lowry base, so it will accept a proton. It will react exactly like limited ammonia, so in limited ammonia you get NH4+, so with the diaminoethane you will get +H3N-CH2-CH2-NH3+ because it accepts the proton.
    Offline

    15
    ReputationRep:
    (Original post by youngar)
    I was wondering if someone could explain 8ei for me? I answered it so that it acted as a ligand on Aluminium but in the mark scheme it acts as a base- how can you distinguish whether it will act as a ligand or a base?
    It gave you a clue in the question. It says 1,2-diaminoethane (en) acts as a base and as a ligand. It then gives you 2 cases, one where it reacts with cobalt (II) ions which is a common question so you you should know that en acts a ligand with Co(II) compounds. The next situation, from the clue in the question you should suspect that en will acts as a base - as a Bronstead-Lowry base and not as a ligand.
    Offline

    20
    ReputationRep:
    (Original post by youngar)
    I was wondering if someone could explain 8ei for me? I answered it so that it acted as a ligand on Aluminium but in the mark scheme it acts as a base- how can you distinguish whether it will act as a ligand or a base?
    Check out the last page of chem revise transition metal notes



    Posted from TSR Mobile
    Offline

    20
    ReputationRep:
    (Original post by B_9710)
    It gave you a clue in the question. It says 1,2-diaminoethane (en) acts as a base and as a ligand. It then gives you 2 cases, one where it reacts with cobalt (II) ions which is a common question so you you should know that en acts a ligand with Co(II) compounds. The next situation, from the clue in the question you should suspect that en will acts as a base - as a Bronstead-Lowry base and not as a ligand.
    One thing I don't understand about this question is that the biddentat ligand does not replace all the waters in aluminium.

    And sorry, I meant page 11 on chem revise


    Posted from TSR Mobile
    Offline

    15
    ReputationRep:
    (Original post by rxns_00)
    Anyone got anything on organic synthesis? I can't deal with it man, I have no clue when it comes to answering a synthesis question lol
    Aye I lav organic synthesis.
    Offline

    8
    ReputationRep:
    (Original post by theboss1998)
    Ok so as a ligand you get full substitution. As a base the diaminoethane acts as brownsted-lowry base, so it will accept a proton. It will react exactly like limited ammonia, so in limited ammonia you get NH4+, so with the diaminoethane you will get +H3N-CH2-CH2-NH3+ because it accepts the proton.
    (Original post by B_9710)
    It gave you a clue in the question. It says 1,2-diaminoethane (en) acts as a base and as a ligand. It then gives you 2 cases, one where it reacts with cobalt (II) ions which is a common question so you you should know that en acts a ligand with Co(II) compounds. The next situation, from the clue in the question you should suspect that en will acts as a base - as a Bronstead-Lowry base and not as a ligand.
    (Original post by Bloom77)
    Check out the last page of chem revise transition metal notes



    Posted from TSR Mobile

    Thank you all, but I think I'm still missing something... I understand that it can act both as a base and as a ligand but why does it act as a base in this case? en is in excess so I assumed it would be a ligand.


    Edit: okay ignore me, aluminium doesn't undergo ligand exchange with ammonia so it wouldn't with this either... Silly me haha.
 
 
 
  • 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
    Brussels sprouts
  • 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.