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    (Original post by Abdulla)
    [Al(OH)6]- and [Al(OH)6]3- are both correct.
    Do you mean [Al(OH)4]-?
    Thanks so much!
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    Do we have to learn the redox titration equations as well? For example the one with MnO4 and Fe.
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    Does anyone know if it is worth learning the equations on page 237 regarding the carbonate ion? I did learn them before but forgotten them, I've just not seen them in exam questions.
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    hi guys anyone fancy explaining an answer to question 2b on the specimen paper

    using a born haber cycle, a value of -905kJ/mol was determined for the lattice enthalpy of silver chloride. a value for the lattice enthalpy of silver chloride using the ionic model was -833kJ/mol
    Explain what a scientist would be able to deduce from a comparison of these values?
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    hi help needed!

    just wondering how this question is calculated.

    A chemical company has a waste tank of volume 25 000 dm
    3
    . The tank is full of
    phosphoric acid (H3PO4) solution formed by adding some unwanted phosphorus(V)
    oxide to water in the tank.
    A 25.0 cm
    3
    sample of this solution required 21.2 cm
    3
    of 0.500 mol dm
    –3
    sodium
    hydroxide solution for complete reaction.
    Calculate the mass, in kg, of phosphorus(V) oxide that must have been added to the
    water in the waste tank. jan 2010 paper
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    hey has anyone got a cgp revision guide?
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    (Original post by Thisisj)
    hey has anyone got a cgp revision guide?
    I do.. How come?
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    (Original post by Sparkly-Star)
    Does anyone know if it is worth learning the equations on page 237 regarding the carbonate ion? I did learn them before but forgotten them, I've just not seen them in exam questions.
    There was a carbonate one with a 3+ transition metal in Jan 2011
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    (Original post by Abdulla)
    Does anybody have the Jan11 QP they can upload? Thanks
    http://www.a-levelchemistry.co.uk/AQ...ary%20home.htm

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    Do we need to know the reactions of period 3 elements with Chlorine? :/
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    (Original post by strawberry_cake)
    I do.. How come?
    do you like it??
    Ive just been looking at a few pages on the cgp website and its soo clear and concise
    I want it but the exam is tomorrow
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    (Original post by strawberry_cake)
    Do we need to know the reactions of period 3 elements with Chlorine? :/
    Nope
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    (Original post by jwest)
    hi guys anyone fancy explaining an answer to question 2b on the specimen paper

    using a born haber cycle, a value of -905kJ/mol was determined for the lattice enthalpy of silver chloride. a value for the lattice enthalpy of silver chloride using the ionic model was -833kJ/mol
    Explain what a scientist would be able to deduce from a comparison of these values?
    The Ag-Cl bond is slightly covalent due to the high difference in electronegativity. The lone pair of electrons are pulled away from the Cl and towards the Ag, thus why the enthalpy change is higher (less negative). The born-haber cycle assumes everything is an ion and there is no covalent.
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    (Original post by Thisisj)
    do you like it??
    Ive just been looking at a few pages on the cgp website and its soo clear and concise
    I want it but the exam is tomorrow
    well don't get it then?????????:confused:
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    (Original post by AminaJB)
    hi help needed!

    just wondering how this question is calculated.

    A chemical company has a waste tank of volume 25 000 dm
    3
    . The tank is full of
    phosphoric acid (H3PO4) solution formed by adding some unwanted phosphorus(V)
    oxide to water in the tank.
    A 25.0 cm
    3
    sample of this solution required 21.2 cm
    3
    of 0.500 mol dm
    –3
    sodium
    hydroxide solution for complete reaction.
    Calculate the mass, in kg, of phosphorus(V) oxide that must have been added to the
    water in the waste tank. jan 2010 paper
    Write an equation for NaOH and H3PO4
    3NaOH + H3PO4 ---> Na3PO4 + H320

    Calculate the number of moles of NaOH and therefore moles of H3PO4
    21.2 x 0.5 / 1000 = 0.0106 moles of NaOH
    It reacts 3 : 1 so divide by 3
    3.53 x10^-3 moles of H3PO4 in 25 cm^3

    Work out the number of moles in 25 dm^3
    3.53 x10^-3 x 25000000 = 3533.3 moles of h3PO4

    Work out the number of moles of P4010
    P4010 + 6H20 ---> 4H3PO4
    Reacts 1 : 4 so divide by 4
    Therefore 883.3 moles of P4O10

    m = n x Mr
    m = 883.3 x 284
    m = 2508572 g

    m = 250.9 kg
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    (Original post by Thisisj)
    do you like it??
    Ive just been looking at a few pages on the cgp website and its soo clear and concise
    I want it but the exam is tomorrow
    ohh its really good hmm I really liked it for mod4, it really helped me learn the stuff because NT was just too confusing,..Anything specific you want? I can copy out some stuff for you if you want?
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    (Original post by Sparkly-Star)
    No need to know it.
    It's Yellow. I have a list of colours off the Chief Examiner since they're obviosly colourblind.. but it's on the list?
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    (Original post by AminaJB)
    hi help needed!

    just wondering how this question is calculated.

    A chemical company has a waste tank of volume 25 000 dm
    3
    . The tank is full of
    phosphoric acid (H3PO4) solution formed by adding some unwanted phosphorus(V)
    oxide to water in the tank.
    A 25.0 cm
    3
    sample of this solution required 21.2 cm
    3
    of 0.500 mol dm
    –3
    sodium
    hydroxide solution for complete reaction.
    Calculate the mass, in kg, of phosphorus(V) oxide that must have been added to the
    water in the waste tank. jan 2010 paper
    Refer to post 574
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    (Original post by jwest)
    hi guys anyone fancy explaining an answer to question 2b on the specimen paper

    using a born haber cycle, a value of -905kJ/mol was determined for the lattice enthalpy of silver chloride. a value for the lattice enthalpy of silver chloride using the ionic model was -833kJ/mol
    Explain what a scientist would be able to deduce from a comparison of these values?
    Assuming atoms are perfect spheres, the lower value for the lattice enthalpy shows that silver chloride is not perfectly ionic and shows covalent character. The lattice is partially polarised.

    Hope this helps.
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    Can someone pleaseeeeeeeee help me with q8c in the jan10 paper??
 
 
 
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