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    (Original post by hahaff)
    did anyone get 53.7 for the percentage for the dichromate question
    i got 70% :s. i know its wrong cuz i got my ratios muddled up..
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    (Original post by hahaff)
    i think i did but i cant really remember
    u knw for the first question was it out of 7 marks
    i think i got -51..

    u had to change the sign for the lattice formation because you need to dissociate the lattice before we can hydrate (or put it on solution) it...
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    For the first question, it asked enthalpy of LATTICE formation, not just formation right?
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    (Original post by Betsss)
    For the first question, it asked enthalpy of LATTICE formation, not just formation right?
    yeah lattice
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    Latice enthalpy forms a SOLID IONIC LATTICE. Think u cant just put compound.

    Ur definition of hydration is actually the definition of the enthalpy of solution?

    Does a H-F bond experience hydrogen bonding?
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    (Original post by Zakir)
    Latice enthalpy forms a SOLID IONIC LATTICE. Think u cant just put compound.

    Ur definition of hydration is actually the definition of the enthalpy of solution?

    Does a H-F bond experience hydrogen bonding?
    so enthalpy of lattice formation: enthalpy change when one mole of the ionic solid, calcium fluoride, is formed from its gaseous ions?
    and enthalpy of hydration: enthalpy change when one mole of separated gaseous fluoride ions are dissolved in water, forming a mole of aqueous fluoride ions?
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    Yh thats right...jus realised i forgot to mention calcium and fluorine in the hydration one!
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    (Original post by kabolin)
    i wrote zn2+??????????????????
    I think it is Zn as it can be oxidised to Zn2+ and so is the reducing agent effectively
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    (Original post by Zakir)
    Yh thats right...jus realised i forgot to mention calcium and fluorine in the hydration one!
    i dont think it matters, just one mark, so they're just looking for gaseous ions to aqueous ions
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    (Original post by Liron Ingleby)
    yes i got +33.6 orsomethingand KJmol^-1 where is this 20.5 coming from?

    thought it was mixed ok in parts hard in others. i think i messed up the whole fuel cell question and made silly mistakes but i only need 89 UMS for an A
    Yeah pretty much the same as you What do you mean by the 20.5? And I need a high c
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    (Original post by Betsss)
    Well, i also put hydrogen bonding, and according to chemguide, it seems to be right

    This is from chemguide:

    The hydration of negative ions

    When an ionic substance dissolves in water, water molecules cluster around the separated ions. This process is called hydration.

    Water frequently attaches to positive ions by co-ordinate (dative covalent) bonds. It bonds to negative ions using hydrogen bonds.

    I'm hoping that's what the markscheme wants though!
    nooo! i wrote about H bonds at first, then i crossed it out and wrote something else urgh!
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    (Original post by Zakir)
    i think i got -51..

    u had to change the sign for the lattice formation because you need to dissociate the lattice before we can hydrate (or put it on solution) it...
    Think i got this
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    No fluoride ions don't act as a Lewis Base, it doesn't form coordinate bonds with the water. I was under the impression the attraction was electrostatic in nature.
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    Can anyone put the paper up?
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    (Original post by Willyg11)
    Can anyone put the paper up?
    someone said y-day that they do have the paper but they dont have a scanner
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    (Original post by l4ith)
    No fluoride ions don't act as a Lewis Base, it doesn't form coordinate bonds with the water. I was under the impression the attraction was electrostatic in nature.
    What did you put for: why did sodium oxide dissolve to give an alkaline solution?
    and how would you test that Al2O3 had ions?
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    (Original post by Betsss)
    What did you put for: why did sodium oxide dissolve to give an alkaline solution?
    and how would you test that Al2O3 had ions?
    For "why did sodium oxide dissolve to give an alkaline solution?" i put that sodium oxide dissociates in water to form a solution containing 2Na+ + 2OH- ions according to the equation: Na2O + H2O (goes to) 2Na+ + 2OH- . The OH- ions formed contribute to the alkalinity of the resulting sodium hydroxide solution, which has a pH of 14.
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    (Original post by loukas2993)
    For "why did sodium oxide dissolve to give an alkaline solution?" i put that sodium oxide dissociates in water to form a solution containing 2Na+ + 2OH- ions according to the equation: Na2O + H2O (goes to) 2Na+ + 2OH- . The OH- ions formed contribute to the alkalinity of the resulting sodium hydroxide solution, which has a pH of 14.
    would i get the marks for saying:
    Na2O is a soluble basic oxide, which dissolves in water to give NaOH (giving an equation), which gives a pH of 14?
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    (Original post by Betsss)
    What did you put for: why did sodium oxide dissolve to give an alkaline solution?
    and how would you test that Al2O3 had ions?
    Sodium oxide will dissolve to give O2- ions. O2- ions are strong bases and attract protons readily, thus pulling a proton from a water molecule and making OH- ions, giving it an alkali pH.

    And I said melt it and test for conduction.
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    (Original post by l4ith)
    Sodium oxide will dissolve to give O2- ions. O2- ions are strong bases and attract protons readily, thus pulling a proton from a water molecule and making OH- ions, giving it an alkali pH.

    And I said melt it and test for conduction.
    Woot i also said the melting thing
 
 
 
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