Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Sphere equation?

  1. Oct 24, 2005 #1

    Math Is Hard

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    OK, I'm clueless. I have this one homework problem where I am asked to represent a reaction with a "sphere equation". I have no idea what this is and I can't locate it in my book. Wasn't mentioned during lecture either.
    Does anyone know what this means? :confused:

    Here's the whole problem (maybe it will make sense in context):

    a) write a chemical equation for the complete combustion of ethane.
    b) represent this equation with Lewis structures.
    c) represent this reaction with a sphere equation.
     
  2. jcsd
  3. Oct 24, 2005 #2

    Tide

    User Avatar
    Science Advisor
    Homework Helper

    I think they are asking you to draw a picture of the reaction using spheres to represent the atoms of each molecule.
     
  4. Oct 24, 2005 #3

    Math Is Hard

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    hey Tide - thanks for responding. Do you mean kinda like a ball and stick diagram?
     
  5. Oct 24, 2005 #4

    Tide

    User Avatar
    Science Advisor
    Homework Helper

    Yes - but without the sticks!
     
  6. Oct 24, 2005 #5

    Math Is Hard

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

  7. Oct 25, 2005 #6

    Chronos

    User Avatar
    Science Advisor
    Gold Member

    Use x^2 + y^2 + z^2 = c to define the boundaries of spherical surfaces.
     
  8. Oct 25, 2005 #7

    Math Is Hard

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    OK, it seems all she was looking for was a "ball and stick" drawing for each molecule in the reaction, but my space filling representations were acceptable. Darn chemistry! Too much artwork!
     
  9. Oct 25, 2005 #8

    Gokul43201

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    MIH : What you want is called a Newman Diagram or Newman representation. That only tells you the conformational arrangement of atoms in a molecule (like ethane), but can not represent a reaction.

    There's no such thing in chemistry as a sphere equation for a chemical reaction. At best, you can write an equation of state based on a hard-sphere interaction model, but that has nothing to do with this question.
     
    Last edited: Oct 25, 2005
  10. Oct 25, 2005 #9

    Astronuc

    User Avatar
    Staff Emeritus
    Science Advisor

    Description of hard sphere equation.

    http://www.math.rutgers.edu/~lebowitz/PUBLIST/jll.pub_43.pdf


    It would appear that one is to represent the equation of state as:

    p/[itex]\rho[/itex]kT = a([itex]\rho[/itex]) + b([itex]\rho[/itex])/kT + c([itex]\rho[/itex])/(kt)2 + . . .

    or see if this looks familiar

    http://www.zae-bayern.de/ectp/abstracts/maeso1.html [Broken]

    Have you seen the Carnahan-Starling equation yet?

    This might be a question for Gokul.
     
    Last edited by a moderator: May 2, 2017
  11. Oct 25, 2005 #10

    Math Is Hard

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    ahh yes.. Newman Diagrams..
    http://www.sollicitatiegesprek.nl/newman.jpg
    Never heard of 'em!!!!
    umm.. before you guys get too carried away, I should tell you this is a class for NON-science majors. :redface: I am lazy as hell, and want to do the LEAST amount of chemistry possible. Here's the description:
    And the book is from our friends at The American Chemical Society.
    http://www.chemistry.org/portal/a/c/s/1/acsdisplay.html?DOC=education\curriculum\context.html"
     
    Last edited by a moderator: Apr 21, 2017
  12. Oct 25, 2005 #11

    Gokul43201

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    That's the one !!!

    Newman diagrams are very simple things with a fancy name. It's one of the first things you learn in organic chemistry.

    Here's what one looks like :

    http://www.chem.tamu.edu/organic/Spring2004/Review/Image382.gif [Broken]
     
    Last edited by a moderator: May 2, 2017
  13. Oct 25, 2005 #12

    Math Is Hard

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    hmm.. y'know Gokul, that doesn't look quite as scary as I imagined. I was curious about it, so I found some explanations of the diagrams here:
    http://www.chem.ucalgary.ca/courses/351/Carey5th/Ch03/ch3-diagrams.html
    so if I understood what they said correctly, that intersection in the front (of the diagram you posted) represents one carbon atom, and it has CH3, Br, and H attached to it. Then the circle would be another carbon atom (behind it) that the front one is bonded to, and it has CH3 and two H atoms attached to it.
    http://www.chem.tamu.edu/organic/Spring2004/Review/Image382.gif [Broken]
    So it's kind of like a perspective drawing?
     
    Last edited by a moderator: May 2, 2017
  14. Oct 25, 2005 #13

    Gokul43201

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Yup. That's all it is !
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook