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Edexcel chemistry - unit 2 19th january 2012

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    (Original post by Cetacea)
    What would you observe if you added potassium iodide to conc. sulphuric acid?
    Purple vapour?
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    (Original post by cisne)
    Purple vapour?
    That's correct. There are 2 other main observations though - a smell of bad eggs (from the H2S gas) and a yellow solid may form.

    Next question: Explain why boron trichloride, BCl3, is non-polar despite having polar bonds.
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    hei...do you know the answer to the previous question i asked from the pastpaper?
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    (Original post by Cetacea)
    What would you observe if you added potassium iodide to conc. sulphuric acid?
    smell of rotten eggs (hydrogen sulphide), purple vapour from the iodine and solid yellow sulphur?
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    (Original post by cisne)
    but-2-ene exists as two geometrical isomers, explain why but-2-ene exists as two geometrical isomers. (2 marks)
    this is a question from january 2008,though......i cuouldn't find a simple way to answer this,can anybody help me please?
    because you can have e-z isomerism?

    for example

    remember there is a c=c double bond, your priority group (CH3) can be either on the same side of the c=c bond or can be on the opposite side .

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    (Original post by Cetacea)
    That's correct. There are 2 other main observations though - a smell of bad eggs (from the H2S gas) and a yellow solid may form.

    Next question: Explain why boron trichloride, BCl3, is non-polar despite having polar bonds.
    What's the full equation for the reaction between sulphuric acid and potassium iodide then?

    For the boron trichloride: All ends of the compound from top to bottom, and left to right are slightly negative. So it only relies on dispersion forces?
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    (Original post by James A)
    because you can have e-z isomerism?

    for example

    remember there is a c=c double bond, your priority group (CH3) can be either on the same side of the c=c bond or can be on the opposite side .

    yeah....thanks alot...
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    (Original post by cisne)
    this is something i prepared with the help of my revision guide....my revision guide is really helpful..i'll try to upload more..
    THANK YOUUU SO MUCH!!
    They really helpful
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    (Original post by Cetacea)
    That's correct. There are 2 other main observations though - a smell of bad eggs (from the H2S gas) and a yellow solid may form.

    Next question: Explain why boron trichloride, BCl3, is non-polar despite having polar bonds.
    because the dipoles moments cancel each other out
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    Helllooo
    I'm going through the alcohols topic yeh.. & i came across 2 contracting stuff..
    first of all..would the reaction be affected if we use alcoholic ammonia & just excess ammonia..??
    According to the AS chem blue text book it says
    CH3CH2I + NH3 ---> CH3CH2NH2 + HI

    Where as in the george facer textbook,
    When excess ammonia is used, it forms
    CH3CH2CH2Cl + 2NH3 ---> CH3CH2CH2NH2 + NH4Cl
    & it even says stating HCl as a product of this reaction is a common error in AS ???

    Which one is correct???
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    (Original post by aqua05)
    Helllooo
    I'm going through the alcohols topic yeh.. &amp; i came across 2 contracting stuff..
    first of all..would the reaction be affected if we use alcoholic ammonia &amp; just excess ammonia..??
    According to the AS chem blue text book it says
    CH3CH2I + NH3 ---&gt; CH3CH2NH2 + HI

    Where as in the george facer textbook,
    When excess ammonia is used, it forms
    CH3CH2CH2Cl + 2NH3 ---&gt; CH3CH2CH2NH2 + NH4Cl
    &amp; it even says stating HCl as a product of this reaction is a common error in AS ???

    Which one is correct???
    Both are technically correct but the HI in the first one would go onto react with another NH3 molecule to form NH4I. The overall equation would be the second one.
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    (Original post by NutterFrutter)
    Both are technically correct but the HI in the first one would go onto react with another NH3 molecule to form NH4I. The overall equation would be the second one.
    righhht
    Makes sense !
    Basically in the exam we should write the second equation, isnt it ?!
    Thanksss !
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    (Original post by aqua05)
    righhht
    Makes sense !
    Basically in the exam we should write the second equation, isnt it ?!
    Thanksss !
    Yeah, they'd most likely expect the overall equation in the exam.
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    (Original post by NutterFrutter)
    Both are technically correct but the HI in the first one would go onto react with another NH3 molecule to form NH4I. The overall equation would be the second one.
    btw what resources are you using to study ?
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    (Original post by aqua05)
    btw what resources are you using to study ?
    CGP revision guide and the Edexcel textbook.
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    (Original post by James A)
    smell of rotten eggs (hydrogen sulphide), purple vapour from the iodine and solid yellow sulphur?
    (Original post by James A)
    because the dipoles moments cancel each other out
    Both correct!
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    (Original post by Cetacea)
    Both correct!
    woop woop, we need to fire more questions and make it a big Q&A so we can all revise together
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    (Original post by James A)
    woop woop, we need to fire more questions and make it a big Q&A so we can all revise together
    Name all of the intermolecular forces operating in molecules of propanal.
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    (Original post by Cetacea)
    Name all of the intermolecular forces operating in molecules of propanal.
    so propanal is an aldehyde, therefore NO HYDROGEN BONDS OCCUR, however PERMANENT DIPOLE DIPOLE interactions OCCUR and of course LONDON FORCES OCCURS IN ALL MOLECULES MOLECULES
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    i prefer this unit a lot more then unit1...its more logical and u goota know ur **** for to answer the questions right lol

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