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chem mod qu aqa anyone? please watch

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    hey, im doing my chem 5 and 6 on tuesday, just doing past paper questions now and its not going well and i need an A!!!!!!!!!! grrrrrrr.......... just wondering if anyone can help me with the following question:

    In which of the following molecules do all the atoms lie in the same plane of molecules?
    (i)BCL3
    (ii)HCHO
    (iii)C2H2Br2
    (iv)NH3

    And how do you know?
    any help would be greatly appreciated!
    thanx ppl and good luck with the rest of ur exams everyone!
    :confused:
    oh and whats the difference between hydrolysis and hydration? hmmmmmm........?
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    (Original post by britney)
    hey, im doing my chem 5 and 6 on tuesday, just doing past paper questions now and its not going well and i need an A!!!!!!!!!! grrrrrrr.......... just wondering if anyone can help me with the following question:

    In which of the following molecules do all the atoms lie in the same plane of molecules?
    (i)BCL3
    (ii)HCHO
    (iii)C2H2Br2
    (iv)NH3

    And how do you know?
    any help would be greatly appreciated!
    thanx ppl and good luck with the rest of ur exams everyone!
    :confused:

    BCl3. It's to do with shapes of molecules; because BCl3 has no lone pairs and only 3 chlorines attached to it, its shape is trigonal planar - as the name suggests, all the atoms are in the same plane. NH3 looks like it might be the same, but in reality it has a lone pair of electrons in addition to the 3 Hs; so its shape with respect to charge density is tetrahedral; with respect to atoms it's pyramidal, so not planar.
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    (Original post by britney)
    oh and whats the difference between hydrolysis and hydration? hmmmmmm........?

    Hydrolysis is the actual breaking of bonds using water. Hydration can simply be when the atom/molecule is surrounded by water molecules.
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    you're an angel thanx u! in the mark scheme it says that the answer for that question is (i), (ii) and (iii), any idea bout HCHO? cnt believe im still up revising at this time!!!!!!! r u doing the paper?
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    (Original post by britney)
    you're an angel thanx u! in the mark scheme it says that the answer for that question is (i), (ii) and (iii), any idea bout HCHO? cnt believe im still up revising at this time!!!!!!! r u doing the paper?
    Yup, sorry, just looked for the first one HCHO is also planar: there are only three areas of negative charge because the carbon has a double bond to the oxygen - which only counts as one region of neg charge - and two bonds to two hydrogens. C2H2Br2: the carbons are joined by a double bond and each have two other bonds; so they each have three regions of negative charge, so it's planar. Sorry for missing that!
 
 
 
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