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Edexcel - Chemistry Unit 2 - 4 June 2013 Watch

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    hey guys! what affects the speed at which a halogenoalkane reacts with water? does it matter if it is primary, secondary or tertiary
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    (Original post by charlieejobson)
    hey guys! what affects the speed at which a halogenoalkane reacts with water? does it matter if it is primary, secondary or tertiary
    I think tertiary has the fastest rate via the Sn1 mechanism.

    Does the water have to be acidic ?
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    (Original post by charlieejobson)
    hey guys! what affects the speed at which a halogenoalkane reacts with water? does it matter if it is primary, secondary or tertiary
    depends on whether the halogenoalkane is primary, secondary or tertiary (which affects the mechanism it undergoes).

    Also depends on which halogen is present. The C-I bond is the weakest and the C-F is the strongest.
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    Is permanent dipole-permanent dipole a molecule that has a electronegativity difference of x>0 or does it have to something specific like 0.4?
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    (Original post by geor)
    Sorry I meant to form an alkene, haha.
    oh haha alright. but do we need to know the mechanism of THAT?
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    (Original post by Jayqwe)
    Is permanent dipole-permanent dipole a molecule that has a electronegativity difference of x>0 or does it have to something specific like 0.4?
    no there just need to be a difference, but if the difference in electronegativivty is more than 1.5 it is more ionic bond than covalent.

    hey can someone write the structural formula or tertiary alcohol like 2-methylbutan-2-ol.

    this is the displayed formula
    .................CH(3)
    ....................|
    CH(3)CH(2)---C---CH(3)
    ....................|
    ..................OH

    will the structural formula be, CH(3)C(CH(3))(OH)CH(2)CH(3) ?
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    Guys what apparatus do we have to draw for the collection of a Bromoalkane by reacting Potassium Bromide with Alochol and Acid, is it just reflux or reflux followed by distillation?
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    (Original post by GCSE-help)
    Guys what apparatus do we have to draw for the collection of a Bromoalkane by reacting Potassium Bromide with Alochol and Acid, is it just reflux or reflux followed by distillation?
    Just distillation
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    (Original post by Katy1704)
    Sorry I thought I'd quoted it ? I'm confused on Q17fii on the may 2011 paper. I've looked at the markscheme and examiners report but I'm not sure what apparatus it is looking for? Thanks
    Questions are different to their numbers... I use my phone so it's hard unless there's an actual question. I would draw this Name:  ImageUploadedByStudent Room1370093537.764792.jpg
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Size:  13.6 KB.


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    (Original post by posthumus)
    Just distillation
    Thanks

    I always get confused about which ones to draw. I know how each one works and the essential knowledge for each one, but there are just so many experiments, it gets muddled up for me
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    (Original post by posthumus)
    Just distillation
    Really? I'm pretty sure you have to reflux it first

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    (Original post by Goods)
    Really? I'm pretty sure you have to reflux it first

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    You can't reflux a distilled product. Once it's distilled, it's in a pure form as it passes through the water condenser at its boiling point. Refluxing is more for carrying out a reaction.

    Reflux is more for the reaction going to completion. The question will tell you everything you need to know.
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    (Original post by Goods)
    Really? I'm pretty sure you have to reflux it first

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    Not sure then, in the george facer book it only suggests you distill off the bromoalkane as it is produced (as it has lower boiling point than the alcohol)


    (Original post by GCSE-help)
    Thanks

    I always get confused about which ones to draw. I know how each one works and the essential knowledge for each one, but there are just so many experiments, it gets muddled up for me
    I feel your pain, I still need to go over aparatus for group 1 & 2 metals whatever it is... & why sometimes stuff needs to be done under water, it has something to do with solubility of gas or something right ?? :confused:
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    (Original post by James A)
    You can't reflux a distilled product. Once it's distilled, it's in a pure form as it passes through the water condenser at its boiling point. Refluxing is more for carrying out a reaction.

    Reflux is more for the reaction going to completion. The question will tell you everything you need to know.
    What? I said reflux then distil which when we did it in class was how we actually did it so...
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    Does dipole mean having a slightly negative atom and a slightly positive atom in a molecule.
    Thanks
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    (Original post by Goods)
    What? I said reflux then distil which when we did it in class was how we actually did it so...
    Yh you could do both....

    heat under reflux..... but you'll have some alcohol left in it (not pure)

    So then you can distill it remove the bromoalkane.

    Or you could have distilled it in the first place & done it in 1 step
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    (Original post by Goods)
    What? I said reflux then distil which when we did it in class was how we actually did it so...
    You can distill a refluxed product, but you cant do vice versa. You misunderstood me a little
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    (Original post by James A)
    depends on whether the halogenoalkane is primary, secondary or tertiary (which affects the mechanism it undergoes).

    Also depends on which halogen is present. The C-I bond is the weakest and the C-F is the strongest.

    but for example do tertiary halogenoalkanes always react the fastest with water when doing an sn1 reaction? and then primary always the fastest when doing an sn2?
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    do we need to be able to test for halogenoalkanes?
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    (Original post by posthumus)
    Not sure then, in the george facer book it only suggests you distill off the bromoalkane as it is produced (as it has lower boiling point than the alcohol)




    I feel your pain, I still need to go over aparatus for group 1 & 2 metals whatever it is... & why sometimes stuff needs to be done under water, it has something to do with solubility of gas or something right ?? :confused:
    Wow I wasn't aware of apparatus for Group 1/2 metals? Well apart from testing thermal stability with lime water etc
 
 
 
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