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    (Original post by rolla01)
    what is formed when a solution containing Al3+ is reacted with excess OH-? [Al(OH)4]- or [Al(OH)]3-

    I've seen both
    the book says 4
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    (Original post by flylikeafly)
    what should I revise? Any predicitons
    everything its not that big compared to chem4
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    (Original post by Super199)
    Safe.

    Do you mind explain the strength of the Cl-Cl bond compared to a br-br bond?
    Sure no problem. The Cl atom is smaller compared to bromine and has less electron sheilding due to less shells around the atom. So the attraction between the nuclues of the chlorine atom and the bond pair of electrons is much stronger because the distance between them is smaller. (Think of it like two magnets attracting. The closer they are the stronger they attract and so the harder it is you pull them away from each other).

    Thus the energy required to overcome this force is much greater. So Cl-Cl bond has requires more energy to break than Br-Br bond.
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    (Original post by rolla01)
    what is formed when a solution containing Al3+ is reacted with excess OH-? [Al(OH)4]- or [Al(OH)6]3-

    I've seen both
    Book isn't always right but

    Is say al oh6

    Cause coordination number seems to be based on size of the molecules / atoms so similar size things will have the same coordination number

    So nh3 oh h20 and cn should all have coordination number of 6

    Where cl will have 4
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    If Delta G is less than or equal to 0 do you say that the reaction is feasible or that it is spontaneous? Or does it not matter? I've seen both appear in markschemes so idk :/
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    Only starting to revise tonight, am I doomed?
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    (Original post by lahigueraxxx)
    If Delta G is less than or equal to 0 do you say that the reaction is feasible or that it is spontaneous? Or does it not matter? I've seen both appear in markschemes so idk :/
    i always write both tbh just to make sure
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    (Original post by nutcase13)
    i always write both tbh just to make sure
    Ah okay cool - thanks!
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    (Original post by lahigueraxxx)
    If Delta G is less than or equal to 0 do you say that the reaction is feasible or that it is spontaneous? Or does it not matter? I've seen both appear in markschemes so idk :/
    Feasibility is talking about the likely hood it is going to be spontaneous a requirement is it has to be below 0 for spontaneous reactions however if they ask why it is below 0 and not spontaneous it wants you to talk about high activation energy etc
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    How do you do this question
    June 2012 question 6di
    I thought you can't combine three redox equations?
    Name:  ImageUploadedByStudent Room1466534163.873380.jpg
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Size:  157.0 KB


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    (Original post by Chembio123)
    Only starting to revise tonight, am I doomed?
    If I were you I'd pull an all nighter
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    (Original post by YoloSwagginz)
    Feasibility is talking about the likely hood it is going to be spontaneous a requirement is it has to be below 0 for spontaneous reactions however if they ask why it is below 0 and not spontaneous it wants you to talk about high activation energy etc
    Thanks!
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    (Original post by Bloom77)
    How do you do this question
    June 2012 question 6di
    I thought you can't combine three redox equations?
    Name:  ImageUploadedByStudent Room1466534163.873380.jpg
Views: 69
Size:  157.0 KB


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    You're not combining them, you're finding the ratio

    MnO4- will stay on one side
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    (Original post by Jmedi)
    You're not combining them, you're finding the ratio

    MnO4- will stay on one side
    And how would you do that
    I normally combine them to find the ratio like you know for those maths chem questions at the end


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    (Original post by emma_1111)
    http://filestore.aqa.org.uk/subjects...5-QP-JUN13.PDF
    For 2cii) why do you times 0.0607 by 17.2?
    I used q=mcΔT and ΔH=q/no. mol. q=(4.18/1000)(20)ΔT no. mol is n=m/mr which is n=5/74.6 then sub into second equation 17.2=(20)(4.18/1000)ΔT/0.0607 rearrange and then get an answer of 13.8 and as ΔH is positive its a decrease in temp so do 298-13.8 to get an answer. c is 4.18/1000 to get it into J not KJ hope this helped.
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    http://filestore.aqa.org.uk/subjects...5-QP-JUN13.PDF
    3bi anyone?
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    (Original post by SirRaza97)
    Sure no problem. The Cl atom is smaller compared to bromine and has less electron sheilding due to less shells around the atom. So the attraction between the nuclues of the chlorine atom and the bond pair of electrons is much stronger because the distance between them is smaller. (Think of it like two magnets attracting. The closer they are the stronger they attract and so the harder it is you pull them away from each other).

    Thus the energy required to overcome this force is much greater. So Cl-Cl bond has requires more energy to break than Br-Br bond.
    I thought Br2 had a higher boiling point??
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    http://filestore.aqa.org.uk/subjects...5-QP-JUN12.PDF
    2b? how to calculate the gradient?
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    (Original post by SubwayLover1)
    I thought Br2 had a higher boiling point??
    I'm talking about breaking bonds not intermolecular forces.
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    Just think of it in terms of ΔG=ΔH-TΔS where where ΔG is y T is the value which varies so is x the ΔS is connected to T so is your gradient m and ΔH is you y intercept c. To get the marks all you do is quote the equation and state what each term corresponds to in y=mx+c. Dont know whether this helped or not.
 
 
 
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