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Edexcel Chemistry AS Unit 2- 16th January 2013 Watch

  • View Poll Results: What did you get in the first sitting for the Unit 2 test?
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    (Original post by jojo1995)
    because the equilibrium moves towards the right, but both n204 and 2no2 aRE still present, just more n202 being formed than before so the colour becomes less brown
    sorry this is really muddled
    but the answer is (D) darker brown, instead of (C) paler brown :/
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    (Original post by Weaselmoose)
    Pretty sure at this rate I'll be retaking my retake...

    Is it just me who finds unit 2 harder than unit 4? Maybe because unit 2 is just SO boring
    Yeah I agree, unit 2 was really challenging...
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    (Original post by ChooChooCherry)
    but the answer is (D) darker brown, instead of (C) paler brown :/
    no thats 16 b
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    (Original post by David Tennant)
    Yeah I agree, unit 2 was really challenging...
    Do I sense sarcasm...
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    Help! Why does chloroethane react differently to iodoethane and also why are tertiary halogenoalkanes more reactive than primary halogenoalkanes
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    does this exam start at 8:30 ? & how long is it ?

    Thanks in advance
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    can someone pleaseee help me with an explanation of why thermal stability increases down the group? i know its to do with the charge density increasing, but the questions are usually worth 3 marks? dreading tomorrow!!
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    (Original post by posthumus)
    does this exam start at 8:30 ? & how long is it ?

    Thanks in advance
    Yes it's a morning one and it's an hour and a half
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    (Original post by kittywitty94)
    can someone pleaseee help me with an explanation of why thermal stability increases down the group? i know its to do with the charge density increasing, but the questions are usually worth 3 marks? dreading tomorrow!!
    As you go down the group, the cation gets larger as they have more electrons hence more electron shells, leads to a smaller charge density,(1) leading to less distortion of the anion/less polarisation of the anion electron cloud (1) so it is more thermally stable due to the less distortion (1)
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    (Original post by kittywitty94)
    can someone pleaseee help me with an explanation of why thermal stability increases down the group? i know its to do with the charge density increasing, but the questions are usually worth 3 marks? dreading tomorrow!!
    Thermal stability of Group 2 Carbonates and Nitrates increases down the group because carbonate and nitrate anions are large, so the electron cloud can be distorted in the presence of a positively charged cation (group 2 cation). The Group 2 cation polarises the anion, distorting it. The greater the distortion, the less stable the ion.

    Large cations cause less distortion due to lower charge density and a lower effective nuclear charge (well, when considering only group 2 that is).
    So, further down group 2 charge density/effective nuclear charge decreases, so less distortion to the carbonate/nitrate anion - therefore more stable.
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    (Original post by flightlessbirds)
    As you go down the group, the cation gets larger as they have more electrons hence more electron shells, leads to a smaller charge density,(1) leading to less distortion of the anion/less polarisation of the anion electron cloud (1) so it is more thermally stable due to the less distortion (1)
    thank you!
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    (Original post by ViraLorSami)
    Thermal stability of Group 2 Carbonates and Nitrates increases down the group because carbonate and nitrate anions are large, so the electron cloud can be distorted in the presence of a positively charged cation (group 2 cation). The Group 2 cation polarises the anion, distorting it. The greater the distortion, the less stable the ion.

    Large cations cause less distortion due to lower charge density and a lower effective nuclear charge (well, when considering only group 2 that is).
    So, further down group 2 charge density/effective nuclear charge decreases, so less distortion to the carbonate/nitrate anion - therefore more stable.
    thank youu!
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    Guys do we just need three mechanics? Addition, sn1 and sn2?
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    (Original post by Exams v__v)
    Guys do we just need three mechanics? Addition, sn1 and sn2?
    a classify reactions (including those in Unit 1) as addition,
    elimination, substitution, oxidation, reduction, hydrolysis or
    polymerization
    b demonstrate an understanding of the concept of a reaction
    mechanism and that bond breaking can be homolytic or
    heterolytic and that the resulting species are either free radicals,
    electrophiles or nucleophiles
    c give definitions of the terms free radical, electrophile and
    nucleophile
    d demonstrate an understanding of why it is helpful to classify
    reagents
    e demonstrate an understanding of the link between bond polarity
    and the type of reaction mechanism a compound will undergo
    f describe the mechanisms of the substitution reactions of
    halogenoalkanes and recall those in 1.7.2e and 1.7.3e
    g demonstrate an understanding of how oxygen, O2
    , and ozone,
    O3
    , absorb UV radiation and explain the part played by emission
    of oxides of nitrogen, from aircraft, in the depletion of the ozone
    layer, including the free radical mechanism for the reaction and
    the fact that oxides act as catalysts.
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    Anyone do the exam today??
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    (Original post by abclol3kid)
    Anyone do the exam today??

    I did. it was a good paper worked to my favour, how did you find it??
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    Thought it was fine! Anyone remember answers? 109.5 degrees for the first angle (C-c-c) yes? And butan-1-amine for the name of the amine?
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    (Original post by Sarahnity)
    Thought it was fine! Anyone remember answers? 109.5 degrees for the first angle (C-c-c) yes? And butan-1-amine for the name of the amine?
    I put 109.5 as well. But I wrote butylamine for the other one.
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    Yeah I doubted butan-1-amine was right And the magnesium reacts better with steam because of the Ea?
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    (Original post by Sarahnity)
    Yeah I doubted butan-1-amine was right And the magnesium reacts better with steam because of the Ea?
    I also put butanamine and I googled it when I got home and apparently it's the same thing as butylamine so hopefully we get a mark and yes I put the Ea one for that


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