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Edexcel - Chemistry Unit 2 - 4 June 2013 watch

  • View Poll Results: Which topic(s) are you finding most difficult?
    Shapes of molecules and ions
    11.66%
    Intermediate bonding and bond polarity
    15.95%
    Intermolecular forces
    9.82%
    Redox
    17.79%
    Group 2 & 7
    40.49%
    Kinetics & Equilibria
    14.11%
    Organic Chemistry - Alcohols and Halogenoalkanes
    39.26%
    Mechanisms
    26.38%
    Green Chemistry
    28.83%

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    (Original post by GCSE-help)
    Doesn't the C-Cl bond break heterolytically in sn2 mechanism as well?
    Yes!
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    (Original post by GCSE-help)
    I think it was a tricky paper, especially the multiple choice but i think i went well for me (fingers crossed). I'm sure you all on here did fine too

    I know I lost 2 silly marks for sure, I put flame test for the second part of the testing question even though it asked to avoid using heat *doh*. But I swear all the questions were 1or 2 markers apart from the last one?
    It will be a flame test.
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    (Original post by airheadbuster)
    It will be a flame test.
    This is awesome news to me wow! I thought I got this wrong, didn't they say no heat?
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    (Original post by airheadbuster)
    First one is correct.

    >Cl atom is too big.

    It will be the electronegativity difference between CL and H is not high enough to make hydrogen sufficiently &+. So, there will be no hydrogen bonding in HCl which means it will have lower boiling point.

    Features of dynamic equilibrium:

    1. The rate of forward reaction is equal to the rate of backward reaction.
    2. The concentration of the species on both sides of the reaction will be unchanged.

    IR:

    They absorb IR emitted from Earth's surface and re-radiates it back to Earth, contributing to global warming.
    I got the IR one right!

    Also got the same as you for the dynamic equilibrium
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    (Original post by Goods)
    I'm pretty sure it was sn1 the other point with dynamic equilibrium is that concentrations of reactants are constant

    Was the alternative test a flame test? It said not using acid or by heating... But a flame test uses both it was all I could think of ....


    Posted from TSR Mobile
    We all did flame test for ours, it was the only thing we could think of...
    I think both sn2 and sn1 will be accepted, as it was a secondary halogenoalkane.
    Yep, that make more sense for the dynamic equilibrium!
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    (Original post by GCSE-help)
    This is awesome news to me wow! I thought I got this wrong, didn't they say no heat?
    They actually meant "no decomposition" as the first one asked.
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    (Original post by posthumus)
    Why does NaCl dissolve in water instead of alcohol?
    Why does fullerene dissolve in petrol while graphite and diamond do not?

    There was another question about carbon neutral that I don't think I answered right.

    1) Because of hydration enthalpy
    2) can't remember options
    3) Got this one wrong... forgot to come back to it & the pesticide should have been taken into consideration
    I got these 2 wrong. :mad:
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    (Original post by airheadbuster)
    I got these 2 wrong. :mad:
    Yh the multiple choice was very hard compared to previous ones
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    (Original post by GCSE-help)
    This is awesome news to me wow! I thought I got this wrong, didn't they say no heat?
    I put a flame test as well but I think you can react them with water or chlorine and the reactivity increases down the group, so barium is a more vigorous reaction than magnesium. I feel I've messed up the paper so badly!
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    For the halogenoalkane with NaOH condition (the second one), I said that it has to be heated under reflux.

    But for the elimination condition, I said that it must be dissolved in ethanol. It didn't cross my mind to put 'dissolved in water' for the NaOH (the second condition question below the elimination one). But then again, aren't we assuming that dilute NaOH is dissolved in water?
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    (Original post by geor)
    I think for the first one I said the one about them being molecular and the other one I put because water has stronger intermolecular forces??? But that answer seemed stupid but I didn't like the other options xD


    Posted from TSR Mobile
    I was stuck between that option and the one I chose here.

    But I chose hydration enthalpy because I thought anything can happen in chemistry as long as the energy is payed back So this outweighs endothermic lattice enthalpy.

    MC was very hard though
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    (Original post by geor)
    I'm /hoping/ they will give us one mark I we said flame test and got the colours correct. I suspect a lot of people did this!!


    Posted from TSR Mobile
    Woops
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    (Original post by crazykid0112)
    I put a flame test as well but I think you can react them with water or chlorine and the reactivity increases down the group, so barium is a more vigorous reaction than magnesium. I feel I've messed up the paper so badly!
    How can you tell the difference just from the fact that one reacts more vigorously than the other? :confused:
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    What did you guys put for why an acid is used to prevent hydrolysis of bromine?
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    (Original post by crazykid0112)
    I put a flame test as well but I think you can react them with water or chlorine and the reactivity increases down the group, so barium is a more vigorous reaction than magnesium. I feel I've messed up the paper so badly!
    I don't think they would accept the reaction with water or chlorine.

    When they referred to don't heat, they meant don't carry out thermal decomposition on it.

    Flame test is the best way to distinguish between the two samples.
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    (Original post by airheadbuster)
    Why does NaCl dissolve in water instead of alcohol?
    Why does fullerene dissolve in petrol while graphite and diamond do not?

    There was another question about carbon neutral that I don't think I answered right.
    Fullerene dissolves because it is molecular
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    (Original post by geor)
    What did everyone put for the one in section C about the amount of co2 absorbed and carbonate ions?


    Posted from TSR Mobile
    I said that an increase in carbonate ions shift the equilibrium to the right, to remove the added carbonate ions, therefore decomposition of CO2 increases and hence it's concentration ceases.
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    (Original post by James A)
    I said that an increase in carbonate ions shift the equilibrium to the right, to remove the added carbonate ions, therefore decomposition of CO2 increases and hence it's concentration ceases.
    Me too! What did you put for why is an acid used to prevent hydrolysis?
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    (Original post by geor)
    What did everyone put for the one in section C about the amount of co2 absorbed and carbonate ions?


    Posted from TSR Mobile
    Increasing CO3[2-] concentration makes the equilibrium of the latter reaction shift right. As the conc. of CO2(aq) decreases, in order to restore equilibrium, the former reaction will go in the reverse direction. So, conc. of CO2 gas in the atmosphere will decrease.
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    Did everyone times precentage error by two?
 
 
 
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