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Lewis structure and thermochemistry problems

  1. Aug 28, 2015 #1
    Hi
    I have a few questions that I have been working on but I don't get the right answer.


    After drawing the Lewis dot structure of HOClO2, pick the incorrect statement of the following.
    A. The oxygen bonded to the hydrogen has two lone pairs
    B. the oxygens not bonded to hydrogen have three lone pairs
    C. The O-Cl bonds are all double bonds.
    D. The H-O bond is a single bond
    E. Chlorine has a full octet.

    The right answer is B.
    I have been looking at this and I would have thought that this Lewis structure would be right as it has the lowest formal charge.
    https://upload.wikimedia.org/wikipedia/commons/8/86/Chloric-acid-2D.pngThe [Broken] The formal Charge for all the atoms would be zero.

    If there are only single bonds between the two oxygen and chlorine the formal charge for each of the two oxygen bonded to chlorine would be: 6-6-(1/2)*2=-1
    and for the chlorine it would be: 7-2-(1/2)*6=2

    I would have thought that the incorrect answer is B and E also because the chlorine would then have an expanded octet.

    Am I wrong?
    Isn't the most abundant structure the one with the lowest formal charge?

    I have another question.

    Two solutions, 50.0 mL of 1.00M BaCl2(aq) and 50.0mL of 1.00M Na2SO4(aq), both initially at 21.5 ˚C, are added to a calorimeter with a total heat capacity, after the solutions are added, of 1.10 kJ/˚C and the temperature rises to 22.7˚C. Determine the qrxn per mole of BaSO4(s) formed in the reaction.
    Answer is: -26.4 kJ/mol

    My solution:
    0.05 moles of Ba2+ and 0.05 moles of SO42- make 0.05 mole of BaSO4(s).
    q=n*c*∆T
    q=0.1*1100*1.2=132 Joules per 0.05 moles of BaSO4(s) formed
    132*1/(0.05)=2640 Joule/mole BaSO4.
    What am i doing wrong here?
     
    Last edited by a moderator: May 7, 2017
  2. jcsd
  3. Aug 28, 2015 #2

    Bystander

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    What's the point of multiplying by "0.1?"
     
  4. Aug 28, 2015 #3

    epenguin

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    A-E are not alternatives, so more than one of them can be right. And I think more than one is.
     
  5. Aug 28, 2015 #4
    I thought it was 0.1 as 0.05+0.05=0.1 moles = total moles of reactants.
    But I have figured this one out. it says the TOTAL heat capacity is 1100 joules so q=c*∆T = 1100*1.2=1320 Joules. So 1320 Joules for every 0.05 moles formed 1320*1/0.05=26400 Joules
     
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