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    Has anyone got a list of all the transition metal colours we actually need to know for the exam?? Would be very appreciated! Thanks
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    JUST noticed this!

    In the mark scheme when you have to write the reaction 2I- + S2O8 (2-) ---> I2 + 2SO4 (2-) or the reactions between vanadium(V)oxide and SO2/SO3...

    the mark scheme says instead of the arrow...it has a weird half circle with a line through it :s WHY?! do we have to write this weird symbol in the exam or is the arrow fine?!:confused:
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    (Original post by ncollier4)
    JUST noticed this!

    In the mark scheme when you have to write the reaction 2I- + S2O8 (2-) ---> I2 + 2SO4 (2-) or the reactions between vanadium(V)oxide and SO2/SO3...

    the mark scheme says instead of the arrow...it has a weird half circle with a line through it :s WHY?! do we have to write this weird symbol in the exam or is the arrow fine?!:confused:
    I think it's just a weird thing that happened with the specimen paper mark scheme. The mark schemes for the other papers involving the contact process just have a typical arrow
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    (Original post by ncollier4)
    JUST noticed this!

    In the mark scheme when you have to write the reaction 2I- + S2O8 (2-) ---> I2 + 2SO4 (2-) or the reactions between vanadium(V)oxide and SO2/SO3...

    the mark scheme says instead of the arrow...it has a weird half circle with a line through it :s WHY?! do we have to write this weird symbol in the exam or is the arrow fine?!:confused:
    lols :P
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    Hey, I'm just going over the Ligand Substitution Chapter, and in the Chelation section the book is asking about how many entities are on either side of the equation. What are they :confused:
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    (Original post by GoodOl'CharlieB)
    Hey, I'm just going over the Ligand Substitution Chapter, and in the Chelation section the book is asking about how many entities are on either side of the equation. What are they :confused:
    It's referring to particles. It's like saying NH3 and Cl- are species. Particles are a type of entity.

    I prefer to use the term moles rather than particles though since questions on it tend to use an equation.

    Hope that's cleared things up

    Edit: My explanation might not be true btw. Just a bit of reasoning and googling :P If anyone can correct me then go ahead please
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    OHHHH HAHAHAHA oh my!

    Thannksssssssss for clearing the confusion ;]

    And I notice this thread is not as....fast paced as the BIOL 5/Other biology exams that are happening tomorrow! My guessing is that people are leaving some chem revision until after that exam? ;] Good luck to anyone doing the paper! Its not as tragic as it seems to be believe me
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    (Original post by jimmy303)
    It's referring to particles. It's like saying NH3 and Cl- are species. Particles are a type of entity.

    I prefer to use the term moles rather than particles though since questions on it tend to use an equation.

    Hope that's cleared things up
    Thank you so much that makes so much more sense now, do you use them to show the increase in entropy (chelate effect)?
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    (Original post by Phil McCrakin)
    lols :P
    Shush ;]
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    (Original post by GoodOl'CharlieB)
    Thank you so much that makes so much more sense now, do you use them to show the increase in entropy (chelate effect)?
    Yup. Though the Chelate effect is referring to the increased stability of complexes which is caused by the increase in entropy, not referring to the increase in entropy itself.

    Example time!

    [Cu(H2O)6]2+ + EDTA4- ---> [Cu(EDTA)]2- + 6H2O

    There is an increase in entropy as there is an increase in the number of moles (2 moles on the left to 7 moles on the right) so [Cu(EDTA)]2- is more thermodynamically stable (you're not going to be able to easily reverse the reaction). This happens with all reactions where multidentate ligands substitute unidentate ligands.

    It's like comparing the amount of disorder of bouncy balls in a box.

    10 bouncy balls bouncing in a box is going to be way more chaotic than a box containing one bouncy ball bouncing around.

    You might also want to know if you don't already that the enthalpy change is near zero because the same number and type (coordinate) of bonds are broken as are formed. Hence why entropy change has such an effect. E.g. with the above reaction six coordinate bonds with the six H2O ligands are broken, but six coordinate bonds are formed with EDTA4-

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    (Original post by jimmy303)
    Yup. Though the Chelate effect is referring to the increased stability of complexes which is caused by the increase in entropy, not referring to the increase in entropy itself.

    Example time!

    [Cu(H2O)6]2+ + EDTA4- ---> [Cu(EDTA)]2- + 6H2O

    There is an increase in entropy as there is an increase in the number of moles (2 moles on the left to 7 moles on the right) so [Cu(EDTA)]2- is more thermodynamically stable (you're not going to be able to easily reverse the reaction). This happens with all reactions where multidentate ligands substitute unidentate ligands.

    It's like comparing the amount of disorder of bouncy balls in a box.

    10 bouncy balls bouncing in a box is going to be way more chaotic than a box containing one bouncy ball bouncing around.

    You might also want to know if you don't already that the enthalpy change is near zero because the same number and type (coordinate) of bonds are broken as are formed. Hence why entropy change has such an effect. E.g. with the above reaction six coordinate bonds with the six H2O ligands are broken, but six coordinate bonds are formed with EDTA4-

    Thanks so much!!!! I understand that much better now (I'm adding this to my notes) and I'm liking the bouncy ball analogy :cool:
    Btw you seem well on your way to acing the exam, hope by friday that I can too
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    (Original post by GoodOl'CharlieB)
    Thanks so much!!!! I understand that much better now and also I'm liking the bouncy ball analogy :cool:
    Btw you seem well on your way to acing the exam, hope by friday that I can too
    you're very welcome. I'm sure you'll be more than fine

    Sadly I have a habit of going straight to answering the questions in exams rather than reading the question so I often end up giving the wrong answer :mad: Need to think of a way of forcing myself to read the questions properly.

    I only recently realised the exam is in the morning rather than in the afternoon, shows how on the ball I am
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    in the lattice MgO between the Mg2+ and O2- are there electrostatic force of attraction or ionic bonds.
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    (Original post by kabolin)
    in the lattice MgO between the Mg2+ and O2- are there electrostatic force of attraction or ionic bonds.
    They're the same thing. Ionic bonds are formed from the electrostatic forces of attraction between oppositely charged ions

    Thus you can use either term when talking about ionic lattices.
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    (Original post by jimmy303)
    you're very welcome. I'm sure you'll be more than fine

    Sadly I have a habit of going straight to answering the questions in exams rather than reading the question so I often end up giving the wrong answer :mad: Need to think of a way of forcing myself to read the questions properly.

    I only recently realised the exam is in the morning rather than in the afternoon, shows how on the ball I am
    Lol, at least you have all the content in your head, if you can grasp unit 5 chemistry I can definitely say that you will learn to read by the exam

    Good luck
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    (Original post by Raimu)
    I'm pretty sure both of them are out of 120. 96/120 was 80% on the last paper.
    Yeah, just checked the specification. Heh, looks like I was wrong Sorry about that I'm actually quite glad though, after how hard I found unit 4 last wednesday...

    Hope your revision is going well
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    (Original post by jimmy303)
    For the last three papers an A* (i.e. 90% ums points) has consistently been around 82-84 marks out of 100.
    Thanks. Is Chem4's grade boundaries similar then?
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    good ways to remember the colours of the metal compounds in solution?
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    I really hate chapter 14, does anyone think we'll be asked anything on batteries? If so, what will they ask us?
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    (Original post by jwest)
    good ways to remember the colours of the metal compounds in solution?
    I've got a colour coded poster
 
 
 
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