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    (Original post by Rassam)
    Enthalpy change: when is it products minus reactants and reactants minus products??
    draw a Hess cycle http://www.chemguide.co.uk/physical/...tics/sums.html
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    i just chedcked in the mark schemes and they give full marks for the answer with no working out!
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    (Original post by arvin_infinity)
    Hess law defi !?
    Hess' law: overall enthalpy change for a reaction is the same, irrespective of the route taken (as long as conditions are the same)
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    (Original post by lolo-x)
    Percentage Yield: actual moles of product obtained divided by the expected moles of product all multiplied by 100

    Atom economy: Mr of desired products divided by the sum of Mr of all products x 100


    Percentage yield is really how efficiently the reaction is taking place - is the reaction operating at its maximum potential?

    Atom economy shows you how much useful product you are getting out of all of the products you have got, so it shows you how wasteful your reaction is
    thanks a lot, that makes sense!
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    guys can we say Ea instead of activation energy in the exam?
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    Benefits of
    isomersation
    reforming
    cracking
    ??
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    can anyone explain what Ziegler Natta is? what do we need to know abou it?
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    Hess's Law is killing me.

    Anyone got any links for Green Chem + Boltzmann?
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    Where it doesn't specify how to draw a compound, shall I just draw the displayed formula?
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    How do you find the enthalpy change of formation when they give you the data for enthalpy change of combustion and vice versa?
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    (Original post by patra)
    can anyone explain what Ziegler Natta is? what do we need to know abou it?
    all it says in the spec is that you should know that the catalyst for polyethene production is ziegler-natta
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    (Original post by yesioo)
    Hess's Law is killing me.

    Anyone got any links for Green Chem + Boltzmann?
    my notes?
    Attached Files
  1. File Type: doc CHEMISTRY UNIT 2.doc (325.0 KB, 238 views)
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    (Original post by touran22)
    guys can we say Ea instead of activation energy in the exam?
    i'm not sure, best not to, just in case
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    (Original post by patra)
    can anyone explain what Ziegler Natta is? what do we need to know abou it?

    Ticl3
    60 degrees
    Unbranched polymer ..thats all I remember
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    good luck guys!
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    How well do we need to know the Other uses of Polymer wastes (i.e. Feedstock recycling )?
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    iii) Outline 2 examples where C02 has replaced the need for CFC's.
    • v) What is the method of obtaining decarbonised fuel and show an equation for methane.

    ??
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    GOOD LUCK everyone!!! x x
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    Good Luck.. x
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    How do you find the enthalpy change of formation when they give you the data for enthalpy change of combustion and vice versa?
 
 
 
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