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    hey guys,

    does any one no which way around the lattice enthalpy arrow goes in the enthalpy cycle because chemical ideas has it pointing up and the june 2010 paper has it pointing down
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    (Original post by RayM)
    It says in the specification:
    'suggest and explain in terms of intermolecular bonds, ionic attractions, and covalent bonding, how some dyes attach themselves to fibres'
    How much detail do we need to know this in and what are the basics because I have no idea :confused:
    Thanks
    Well i think you have 4 types of dye. Direct dye, mordant, acid dye and fibre reactive dyes.

    direct dye attach to cotton with hydrogen bonds between dye molecule and fibre.

    mordant. Metal ion which Forms a complex with the dye and the fibre have dative covalent bonds to the metal ion.

    acid dye. Ionic bonds between protein fibre and dye molecule

    fibre-reactive have strong covalent bonds with cotton fibres
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    (Original post by dan1993)
    hey guys,

    does any one no which way around the lattice enthalpy arrow goes in the enthalpy cycle because chemical ideas has it pointing up and the june 2010 paper has it pointing down
    I think it is down seen as the defination is the enthalpy change when 1 mole of a solid is formed from its gaseous ions.
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    (Original post by JamesPen)
    Can i confirm that a dehydration of a alcohol to an Alkene is conc H2S04 refluxed??
    Conc. H2SO4 followed by water I thought

    Although I remember the water, Phosphoric acid catalyst, 300C and 60atm method
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    (Original post by dan1993)
    hey guys,

    does any one no which way around the lattice enthalpy arrow goes in the enthalpy cycle because chemical ideas has it pointing up and the june 2010 paper has it pointing down

    lattice enthalpy is down (gas to solid)

    but when you use it in the equation:

    /\Hsoln = -/\Hle + (/\Hhyd(anion) + /\Hhyd(cation))

    it is up in that you are reversing the lattice enthalpy to get from solid to gas, then gas to aq ions in solution, to calculate /\Hsoln. Like in AS when you reversed the arrow in Hess' Law

    hope this helps, its the only way i understand it
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    (Original post by JamesPen)
    I think it is down seen as the defination is the enthalpy change when 1 mole of a solid is formed from its gaseous ions.
    yeah that make sense thanks mate
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    (Original post by RayM)
    It says in the specification:
    'suggest and explain in terms of intermolecular bonds, ionic attractions, and covalent bonding, how some dyes attach themselves to fibres'
    How much detail do we need to know this in and what are the basics because I have no idea :confused:
    Thanks
    It'll just be giving you molecular structures of dyes and fibres.

    And then it'll say how can these bond? Draw in the bonds.

    Or it'll be 'Identify these bonds'.

    And it'll only be, id-id, perm dipole, hydrogen, ion-dipole, ionic, covalent bonds.
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    (Original post by joestevens2092)
    Conc. H2SO4 followed by water I thought

    Although I remember the water, Phosphoric acid catalyst, 300C and 60atm method
    No, for dehydration no water is added. For hydration you need to add water after the refluxing with conc. H2SO4.
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    (Original post by JamesPen)
    Can i confirm that a dehydration of a alcohol to an Alkene is conc H2S04 refluxed??
    Yes it is.
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    (Original post by AGM)
    No, for dehydration no water is added. For hydration you need to add water after the refluxing with conc. H2SO4.
    I've gone the opposite way, silly me
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    (Original post by Boompw)
    What are the conventions for labelling an energy level diagram there were some in the Jan 11 paper.

    Is the y axis labelled energy or enthapy, or does it not matter?

    And do you label each energy level, energy level 1, 2, 3 etc.?
    I think it's labelled energy. Enthalpy is the energy per mole. When you're talking about electrons I'd have thought that you would be talking energy for one specific electron.
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    (Original post by 41jms)
    anyone know about molecular recognition?
    If I remember correctly that's just stuff to do with molecules such as substrates for proteins and (more contextually) neurotransmitters at nerve endings.

    Just know that the size, shape and available bonds (bond configuration) are all at play with this molecular recognition malarkey! :rolleyes:
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    Has anybody got the Jan 2010 mark scheme? I can't find it anywhere.
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    here you go
    Attached Images
  1. File Type: pdf Jan 2010 Mark Scheme Chemistry By Design.pdf (325.1 KB, 710 views)
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    Reactions of carboxylic acids always get me
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    It's going to be pot luck if I can answer any synthesis reagents and conditions.. There's soooo many..
    • Thread Starter
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    Good Luck for tomorrow EVERYONE!!
    gonna have an early night
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    (Original post by gozatron)
    It's going to be pot luck if I can answer any synthesis reagents and conditions.. There's soooo many..
    Despite having sheets of all of the reactions and conditions taped to my wall, I still can't remember any of them and I think I've recognized my fate if/when 'that' question comes up...
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    (Original post by JamesPen)
    Well i think you have 4 types of dye. Direct dye, mordant, acid dye and fibre reactive dyes.

    direct dye attach to cotton with hydrogen bonds between dye molecule and fibre.

    mordant. Metal ion which Forms a complex with the dye and the fibre have dative covalent bonds to the metal ion.

    acid dye. Ionic bonds between protein fibre and dye molecule

    fibre-reactive have strong covalent bonds with cotton fibres

    sheeeeeeeeet do we need to know this?
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    (Original post by 41jms)
    sheeeeeeeeet do we need to know this?
    I hope not. -.-'

    If a question that's not to do with the azo reactions and is something out of Storylines (I think this stuff was in there...) then I'm just going to hope that righting down something like '...errr...ionic? Mordant?...Marks, please? ' will work. :rolleyes:
 
 
 
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