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    Anyone know how to rearrange the equation if they ask you to work out the hydration enthalpy and you have enthalpy of sol already?
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    How do you generally do those 5 mark calculation questions
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    Does anyone know if all the oxides form a protective insoluble layer or is it just MgO and Al2O3
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    (Original post by SirRaza97)
    It's 1:2.9, not 1:3. The reason for that is the next part of the question
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    What's the oxidation state of cobalt in this

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    I seem to be getting +2 but the answers +3

    I did:
    Co + 1 - 4 = -1
    Co = + 2


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    (Original post by zombaldia)
    A lot of chemistry is just trying to simplify it. At least for me anyway. Try use notes on chemrevise for chem5 if you would like some good notes
    It's where I wrote my notes up from (along with AQA textbook) - I must've missed that! Thanks
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    (Original post by ninjaduck)
    It's 1:2.9, not 1:3. The reason for that is the next part of the question
    Well that's kinda stupid. Oh well 1:2.9 then
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    (Original post by Bloom77)
    What's the oxidation state of cobalt in this

    Name:  ImageUploadedByStudent Room1466526474.262787.jpg
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    I seem to be getting +2 but the answers +3

    I did:
    Co + 1 - 4 = -1
    Co = + 2


    Posted from TSR Mobile
    think about the overall charge. Its (CoO2)- oxygen has an oxidation state of -2. 2 times -2 = -4.

    therefore cobalt has to be+3, as -4+3 = -1
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    (Original post by flylikeafly)
    Does anyone know if all the oxides form a protective insoluble layer or is it just MgO and Al2O3
    I would've guessed all of them, however you only need to know Al2O3 (MgO is given in questions)
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    (Original post by Bloom77)
    What's the oxidation state of cobalt in this

    Name:  ImageUploadedByStudent Room1466526474.262787.jpg
Views: 123
Size:  131.5 KB

    I seem to be getting +2 but the answers +3

    I did:
    Co + 1 - 4 = -1
    Co = + 2


    Posted from TSR Mobile
    You only need to look at the compund in the square brackets Oxygens = -4 and to get -1 overall charge it's +3
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    (Original post by jammypancake)
    Anyone know how to rearrange the equation if they ask you to work out the hydration enthalpy and you have enthalpy of sol already?
    Depends if you're giving lattice formation or dissociation. I always draw it out but this is how you do it if given dissociation.

    sol=dissociation+hydration enthalpies

    simply rearrange to get hydration=sol-dissociatiation-other hydration you are given
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    (Original post by sirraza97)
    thanks!!!!!!! Genius
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    Does anyone here know exactly which colours we have to know for transition metals in this exam? ive learnt most of the common ones
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    Is lattice dissociation always -ve?
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    (Original post by GO97)
    Does anyone here know exactly which colours we have to know for transition metals in this exam? ive learnt most of the common ones
    learn all of them. Seriously it'll only take an hour in total. If you repeat them to urself maybe every hour then they should be in your head. They could ask anything and especially with how chem 4 was I don't think you should leave the memory part down to chance.
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    (Original post by emma_1111)
    Is lattice dissociation always -ve?
    it should be positive? since energy is supplied to break the lattice
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    (Original post by emma_1111)
    Is lattice dissociation always -ve?
    it's always +ve
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    (Original post by SirRaza97)
    learn all of them. Seriously it'll only take an hour in total. If you repeat them to urself maybe every hour then they should be in your head. They could ask anything and especially with how chem 4 was I don't think you should leave the memory part down to chance.
    like every possible colour? im more than willing to learn every colour on the spec but i dont really have a source to study them, revision guide doesnt give them all and i cant find a useful site. Do you have any recommendations?
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    Thanks guys! ^^^^^


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    can someone list down all the cells we need to know
 
 
 
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