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    (Original post by MrVagina)
    Ive only just found it on a 2011 paper but its not in my revision guide, do we have to know the reaction of halogens with cyclohexane? if so can anyone tell me what they are
    yeah you do, a Cl2 turns the organic solvent layer light green, Br2 turns it orange and I2 turns it purple
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    Does anyone know where to get the January 2013 unit 1 and 2 papers from? (and mark scheme)? thank you!
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    (Original post by Angelicaaa)
    Does anyone know where to get the January 2013 unit 1 and 2 papers from? (and mark scheme)? thank you!
    Someone posted the unit 1 ones on here a few pages back I think!
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    Can anyone explain why carbon12 is the standard?
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    pretty sure you dont need to know why its standard
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    (Original post by Ardey1234)
    Can anyone explain why carbon12 is the standard?
    The book only says because it's a compromise between the physicists and chemists as they were originally using different oxygen isotopes. But they are unlikely to ask why
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    What're the definitions we need to know for 'amount of substance', 'mole' and 'Avogadro's constant'?
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    (Original post by Ingamo)
    Someone posted the unit 1 ones on here a few pages back I think!
    Thank you! Ahh I can't find it :confused:
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    (Original post by Angelicaaa)
    Ahh I can't find it :confused:
    Pg 2
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    (Original post by HelenPaddock)
    Pg 2
    Thank youu!
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    (Original post by zangorou)
    What're the definitions we need to know for 'amount of substance', 'mole' and 'Avogadro's constant'?
    Amount of substance is the measure of the amount of entities in a expressed in moles.

    A mole is a amount of a substance which contains as many atoms as in 1/12th of carbon 12.

    Avogadro's constant is 6.0225 x 10^23
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    Wondering if someone could help me?

    The question is:
    Suggest the formula of sodium chlorate(VII).

    I know its something to do with oxidation numbers... or something... :P
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    (Original post by Ardey1234)
    Can anyone explain why carbon12 is the standard?
    Don't take my word for it, but I think it's because carbon-12 is a stable isotope of carbon and it is rarely found as an other isotope. As opposed to other elements where different isotopes may be more common.
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    (Original post by theCreator)
    Don't take my word for it, but I think it's because carbon-12 is a stable isotope of carbon and it is rarely found as an other isotope. As opposed to other elements where different isotopes may be more common.
    Yh. Think you're right. I would of gone with its the most abundant isotope of carbon.

    Thanks man
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    (Original post by jo7777)
    Wondering if someone could help me?

    The question is:
    Suggest the formula of sodium chlorate(VII).

    I know its something to do with oxidation numbers... or something... :P

    I think it's NaCl04, because we know the chlorine has an oxidation number of 7. Chlorate means it is made up of chlorine and oxygen, and oxygen commonly has an oxidation number of 2. So in order to get an overall oxidation number of -1 (so that it reacts with the Na 1+ ion). There needs to be 4 oxygens.
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    explain why fluorine has low boiling point?

    why does NF3 have a permanent dipole?
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    (Original post by theCreator)
    I think it's NaCl04, because we know the chlorine has an oxidation number of 7. Chlorate means it is made up of chlorine and oxygen, and oxygen commonly has an oxidation number of 2. So in order to get an overall oxidation number of -1 (so that it reacts with the Na 1+ ion). There needs to be 4 oxygens.
    Ahhh yes I get it, thanks.

    Also, I hate the questions where it states two elements such as Magnesium and chlorine, and then says that magnesium's melting point is higher...
    Then it asks you to explain why.
    I understand that magnesium has metallic bonding, and chlorine has covalent bonding... but how do I know whether or not it has giant covalent or simple covalent.

    And why does the mark scheme say that only the Cl has van der waals? I thought all molecules had van der waals...

    Bit confused
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    (Original post by ii-mohsin-ii)
    explain why fluorine has low boiling point?

    why does NF3 have a permanent dipole?
    Fluorine exists as a simple molecule. So there are only weak van der waal's forces between molecules which are weak and require a small amount of energy to break.

    NF3 has permanent dipoles because Fluorine is more electronegative than Nitrogen. So it attracts the shared pair of electrons more creating a permanent dipole. The overall molecule is polar therefore since NF3 has an unsymmetrical shape and the dipoles would not cancel each other out.
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    (Original post by ii-mohsin-ii)
    explain why fluorine has low boiling point?

    why does NF3 have a permanent dipole?
    Bonds intermolecularly (as F2) via van der Waals' forces which are easy to break.

    It's non symmetrical (trigonal pyridimal).
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    (Original post by jo7777)
    Wondering if someone could help me?

    The question is:
    Suggest the formula of sodium chlorate(VII).

    I know its something to do with oxidation numbers... or something... :P
    Yeah, the Roman numerals refer to the oxidation state of the chlorine. Oxygen has an oxidation state of -2 and sodium has an oxidation state of +1. So it must be the chlorine that has a +7 oxidation state. And, as it's neutral overall, the formula would be... Hope that helped!

    Kind of worrying about this exam. It's a resit from January for me. I'm worried because I understand all of this stuff but only managed a C in the exam. Going through past papers, I can see nothing that poses a huge threat, but my confidence isn't there purely based on my performance in January. Here's hoping my exam technique is good enough now for me to be able to answer the questions better.

    EDIT: dammit, late to this party :P Hope it helped alongside everyone else's answers, haha! Good practice for me, too
 
 
 
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