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Homework Help: Ion IO3- and CHCl3 questions

  1. Mar 11, 2018 #1

    Physics345

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    1. The problem statement, all variables and given/known data

    For the ion IO3 –

    a) Draw the electron dot diagram and structural formula using the method as taught in this course.

    b) Predict the shape.

    c) Predict whether it is polar or non-polar, justify your prediction. Indicate the positive and negative poles.

    For the ion CHCl3

    a) Draw the electron dot diagram and structural formula using the method as taught in this course.

    b) Predict the shape.

    c) Predict whether it is polar or non-polar, justify your prediction. Indicate the positive and negative poles.


    2. Relevant equations
    none

    3. The attempt at a solution
    ZIUpkpv.png
     
  2. jcsd
  3. Mar 11, 2018 #2
    And your question is...?
     
  4. Mar 11, 2018 #3

    Physics345

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    Did I do this correctly?
    I kind of rewrote my answer, this seems more accurate.
    GstDhwh.png
     
  5. Mar 11, 2018 #4
    Sorry I deleted the previous post. Btw now I think it is correct.
     
  6. Mar 11, 2018 #5
    CHCl3 was wrong in the previous image

    ps: since I'm not an expert, I'd like for someone more competent to check answer c) for IO3-. It seems fine to me, but I don't feel enough prepared to confirm.
     
  7. Mar 11, 2018 #6

    Physics345

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    I appreciate your reply, but I need certainty, I need to learn from my mistakes "I think it is correct" is too vague, it will make me insecure about my knowledge/understanding of this topic. I'm not devaluing your reply, but it's not a confident answer. Hopefully others will chime in and we can confirm, but thank you, your help is very much appreciated.
     
  8. Mar 11, 2018 #7

    Physics345

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    Oh, you beat me to it! I appreciate it.
     
  9. Mar 11, 2018 #8
    Yeah sorry, I studied these stuff (and I probably will again) but it has passed some time since the last time I used to think about it so I don't feel so comfortable anymore
     
  10. Mar 11, 2018 #9

    Ygggdrasil

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    In general, the answers look correct, though the explanation could be a bit more clear.
    IO3- has three bonds, so describing IO3- as a polar covalent bond is unclear. The I-O bonds are polar covalent bonds because of the electronegativity difference between the two atoms (which results in an unequal distribution of electrons).

    This explanation is not correct. The electrons being shared unequally by the two atoms in a bond result in an electric dipole. Because IO3- has three bonds, there are three such dipoles that compose the molecule. It is the geometry of the molecule that determines whether the dipoles would cancel (e.g. if the molecule were trigonal planar rather than trigonal pyrimidal, the dipoles from the three I-O bonds would cancel and the molecule would be non-polar despite being composed of three polar covalent bonds). You can think of the dipole moments from each of the I-O bonds as a vector pointing in the direction of the I-O bond. To determine the overall dipole moment of the molecule, you sum those three vectors to see to whether they cancel each other or combine additively.

    Your drawing does a good job of showing why the individual dipole moments of the three I-O bonds do not cancel and result in the molecule retaining a net dipole moment.

    This is correct.
     
  11. Mar 11, 2018 #10

    Physics345

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    Okay I've been studying/writing out assignments for that last 15 hours. I think it's time for bed that's enough fun for today I managed to reply to the other two threads before heading to bed I will adjust my answer for this tomorrow as well. I'll adjust my answer as soon as I wake up and finish writing, good night and thanks again!
     
  12. Mar 12, 2018 #11

    Physics345

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    I adjusted my answer according to your comments for part c) for IO3- also is CHCl3 fine?
    c) IO creates three polar covalent bonds from each oxygen atom to the center atom Iodine.Oxygen is more electronegative than Iodine leading to an unequal distribution of electrons -1 +1+1+1= +2 therefore the Iodine end is slightly negative and the oxygen end is slightly positive.
     
    Last edited: Mar 12, 2018
  13. Mar 12, 2018 #12

    mjc123

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    Is that true?
     
  14. Mar 12, 2018 #13

    Physics345

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    Opps that was a typo good catch.
     
  15. Nov 9, 2018 at 6:38 PM #14
    Ok i'm confused could some one please clarify something for me,


    The drawing stated that the oxygen end was slightly more positive while the Iodine end is slight more negative. But the electronegativity of oxygen is 3.4 while Iodine is 2.6. Which means electrons will be pulled towards oxygen since it is more electronegative, thus the arrow would be pointing towards oxygen making the oxygen end negative and the iodine end positive.

    Am i correct or do I have it all wrong?
     
  16. Nov 9, 2018 at 7:04 PM #15

    Ygggdrasil

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    Yes, you are correct. Oxygen is more electronegative than iodine, so the oxygen carry a partial negative charge and the iodine would carry a partial positive charge. In some of the OP's diagrams, this is depicted correctly, and in other this is not.
     
  17. Nov 9, 2018 at 7:34 PM #16
    Thank You so much! So basically, This molecule is polar because first of all the I-O bonds have a difference of 0.8 which makes them polar covalent. Then secondly the overall polarity of the molecule is polar as well because as we can see the shape of the molecule is not symmetrical due to the lone pair on the central atom which means the dipoles don’t cancel eachother out. Therefore the overall polarity of the molecule is polar.

    If for example there was another I-O bond instead of the lone pair on top of Iodide then the overall molecular polarity would be non-polar then.

    Here's a pic for reference:
    20181109_202744.jpg
     
  18. Nov 10, 2018 at 8:25 AM #17

    Ygggdrasil

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    That is a good answer. One suggestion to make the answer more complete would be to describe the geometry of the IO3 ion (there is a particular name for the shape of the ion).
     
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