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Edexcel - Chemistry Unit 2 - 4 June 2013 Watch

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    [Jan 2009]
    8) Which intermolecular forces exist between molecules of ethoxyethane? Name:  ws.jpg
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    A. Instantaneous dipole – induced dipole only
    B. Permanent dipole – permanent dipole only
    C. Instantaneous dipole – induced dipole and hydrogen bonds
    D. Instantaneous dipole – induced dipole and permanent dipole – permanent
    dipole
    The answer is D, but I don't get how ethoxyethane has a permanent dipole. Based on the displayed formula, won't the polar bonds cancel out, making it a non-polar molecule?
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    (Original post by SKK94)
    [Jan 2009]
    8) Which intermolecular forces exist between molecules of ethoxyethane? Name:  ws.jpg
Views: 125
Size:  8.7 KB
    A. Instantaneous dipole – induced dipole only
    B. Permanent dipole – permanent dipole only
    C. Instantaneous dipole – induced dipole and hydrogen bonds
    D. Instantaneous dipole – induced dipole and permanent dipole – permanent
    dipole
    The answer is D, but I don't get how ethoxyethane has a permanent dipole. Based on the displayed formula, won't the polar bonds cancel out, making it a non-polar molecule?
    I don't think the bond polarities cancel out in this one. The delta-negative oxygen molecule is pulling electrons towards itself from two Carbon atoms, so there is a shift in electron density towards the centre, which isn't balanced out.
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    Be cannot react with water or steam due to an oxide layer present on the surface of the metal therefore, be(oh)2 cannot be formed.... so how is it possible the be(oh)2 can react with acids to form salt + water (if be(oh)2 doesn't exist as Be is very unreactive) ??
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    (Original post by GCSE-help)
    I don't think the bond polarities cancel out in this one. The delta-negative oxygen molecule is pulling electrons towards itself from two Carbon atoms, so there is a shift in electron density towards the centre, which isn't balanced out.

    (Original post by geor)
    I think it's because the oxygen has 2 lone pairs..?
    Attachment 221851
    Got it! Thanks!
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    (Original post by geor)
    Attachment 221854
    Why is the answer C? Surely the percentage error would be 0.8% as you are measuring two solutions? Thanks in advance.
    (0.08/20 )*100

    Answer is 0.4%
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    (Original post by geor)
    Attachment 221854
    Why is the answer C? Surely the percentage error would be 0.8% as you are measuring two solutions? Thanks in advance.
    0.08/20 x 100 = 0.4

    its given first as error in volume you need to convert it to a percentage error of the volume
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    Do we need to know the specific reason why solubility trends for hydroxides and sulfate differ down group 2? Like why solubility of magnesium hydroxide is least soluble and there is highest solubility of barium hydroxide whilst magnesium sulfate is most soluble and barium sulfate is least soluble or even insoluble.
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    Can anyone name all de experimental setups dat may come for sketching???
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    Hey!

    Which reactions do we used to show the production of Bromoalkanes and iodoalkanes from an alcohol? does PBr5 and PI5 exist. The textbook says that alcohols react with PCl5 to produce a chloroalkane and corresponding raections occur with the other phosphorous halides. Does that mean they exist?
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    (Original post by Goods)
    Post the question please I can't help without something to answer


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    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
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    (Original post by Kurraiyo)
    Quoting from this book: "You can see that the H-Cl bond will be much more polar than the H-Br or H-I bond so the dipole-dipole interactions will be greater and this will explain the higher boiling temperature." By "higher boiling temperature" they didn't mean higher than the boiling point of HBr or HI, rather they meant that the boiling point of HCl is higher than you might expect if you just extended the graph to predict the boiling point of HCl.
    the permanent dipole-dipole forces are strongest in HCL and get weaker down the group, however the London forces increase as you go down the group, since London forces are considerably stronger than the permanent dipole-dipole forces, the boiling temperature increase as you go down the group.

    it can get tricky sometimes.

    can someone explain the collision theory ? I know the factors that affect the the rate of reaction, and I even know how exactly they do it. but WHAT THE HELL IS COLLISION THEORY ? lol
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    (Original post by felicity95)
    Hey!

    Which reactions do we used to show the production of Bromoalkanes and iodoalkanes from an alcohol? does PBr5 and PI5 exist. The textbook says that alcohols react with PCl5 to produce a chloroalkane and corresponding raections occur with the other phosphorous halides. Does that mean they exist?
    For Bromoalkanes use HBr- made in situ with Br2 and H2SO4 heated under reflux
    For iodoalkanes use PI3
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    (Original post by felicity95)
    Hey!

    Which reactions do we used to show the production of Bromoalkanes and iodoalkanes from an alcohol? does PBr5 and PI5 exist. The textbook says that alcohols react with PCl5 to produce a chloroalkane and corresponding raections occur with the other phosphorous halides. Does that mean they exist?
    For bromoalkanes.

    KBr and 50% Sulphuric acid which produces HBr. This HBr then reacts with the alcohol to produce a bromoalkane.

    Damp red phosphorus reacts with iodine to form PI3. This PI3 then reacts with the alcohol to produce your iodoalkane.

    Forget what the textbook said because they always waffle on. Keep within the exam spec. What I said above are the reactions used (when looking at the mark scheme)
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    (Original post by geor)
    Collision theory
    1) Particle A must collide with particle B.
    2) The particles must possess between them energy greater than the activation energy.
    3) The particles must collide with the correct orientation.
    TY its so easy now
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    (Original post by acer0951)
    Do we need to know the specific reason why solubility trends for hydroxides and sulfate differ down group 2? Like why solubility of magnesium hydroxide is least soluble and there is highest solubility of barium hydroxide whilst magnesium sulfate is most soluble and barium sulfate is least soluble or even insoluble.
    Nope, this is covered in Unit 4 (it's in the A2 George Facer book anyway)... but even for that unit I don't think it's in the spec
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    for the oxidation of primary and secondary alcohols do you have to write the reagents fully or can you just put [o] instead of potassium dichromate(VI) and Sulphuric Acid. ?
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    t
    (Original post by Baraf)
    for the oxidation of primary and secondary alcohols do you have to write the reagents fully or can you just put [o] instead of potassium dichromate(VI) and Sulphuric Acid. ?
    i have a feeling they won't accept simply [o] its best to put the two names just to be on the safe side
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    (Original post by Baraf)
    for the oxidation of primary and secondary alcohols do you have to write the reagents fully or can you just put [o] instead of potassium dichromate(VI) and Sulphuric Acid. ?
    If asked to write an equation for the reaction you can use [o] if asked for what you would add you need to write the reagents fully. We are not expected to know the mechanism of stoichiometry for the equation hence why [o] is acceptable in that situation but not in any others
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    (Original post by MSamuel)
    t

    i have a feeling they won't accept simply [o] its best to put the two names just to be on the safe side
    (Original post by Goods)
    If asked to write an equation for the reaction you can use [o] if asked for what you would add you need to write the reagents fully. We are not expected to know the mechanism of stoichiometry for the equation hence why [o] is acceptable in that situation but not in any others
    cheers for that
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    [O] is absolutely fine. They will allow it. I've seen in past papers.

    I'm assuming you are talking about the written equation.

    if you have to list the reagents, then give the full name of the reagents
 
 
 
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