A Universe from Nothing: Not that hard to understand.

Discussion in 'General Science & Technology' started by paddoboy, Feb 3, 2017.

  1. Write4U Valued Senior Member

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    Is the mass of a molecule different than the sum total mass of the atoms that make up the molecule?
     
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  3. DaveC426913 Valued Senior Member

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    Well, for starters, water - even pure water - is not simply a single molecule.
    It is composed of free hydrogen ions (H+), free hydroxides (OH-) as well as H20.
     
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  5. Write4U Valued Senior Member

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    Thank you, I didn't know that. So in effect, a watermolecule would also include the mass of those free atoms?, in addition to H2O. Is there a fixed number of those particles, or does the term "free" indicate an arbitrary amount contained in a water molecule.?
     
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  7. Write4U Valued Senior Member

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    Link is in post #291
     
  8. exchemist Valued Senior Member

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    But where, in that long Wiki article, is there anything about fundamental symbolic constants? I could not see any reference to these.

    SI is a system if units of measure. A unit of measure is not a fundamental constant. It is an arbitrarily chosen quantity, adopted as a standard for convenience.

    Examples of fundamental constants would be the speed of light, c, or Planck's constant, h. Note that these will have different numerical values depending on the system of units in which they are expressed, e.g. c can be expressed in miles per hour or metres per second, etc.
     
    Last edited: Aug 21, 2017
  9. exchemist Valued Senior Member

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    Not if one neglects the infinitesimally tiny relativistic effect on mass of the bond energies.

    A hydrogen atom has a mass of 1 atomic unit, an oxygen atom a mass of 16 units and thus a water molecule a mass of 18 units.

    A collection of Avogadro's Number of water molecules has a mass of 18g.

    The qualification about relativity and bond energy arises from the fact that the bound state of water lies at lower energy (i.e. is a more stable state) than the isolated hydrogen and oxygen atoms. This would mean that in theory, since it contains less energy than the isolated atoms its mass would be very slightly less, by E=mc². But the difference is so tiny that nobody would ever bother with it.

    (Such differences in energy due to stability can however be significant when one considers the much stronger bonding between protons and neutrons in an atomic nucleus, i.e. in the realm of nuclear physics rather than chemistry.)
     
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  10. exchemist Valued Senior Member

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    Technically true, but perhaps a bit confusing for Write4U, don't you think?

    The dissociation constant for pure water is 10⁻¹⁴, making the concentrations of H30+ and of OH- each equal to 10⁻⁷ (which is why the pH of water is 7).

    So that means only one molecule in every 10 million is dissociated into ions at any given moment.
     
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  11. Xelor Registered Member

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  12. Write4U Valued Senior Member

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    Does this in any way restrict the formation of bio-chemicals? We are talking about probabilistic events over enormous time spans, by trillions per second throughout the universe.

    Unless someone can prove that mathematically something cannot occur, I remain optimistic that no matter how we hard try to imitate nature in a lab, it has already been there and done that, long before we came on the scene. IMO
     
    Last edited: Sep 6, 2017
  13. exchemist Valued Senior Member

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    No.
     
  14. Nahor87 Registered Member

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    E=mc2
     
  15. DaveC426913 Valued Senior Member

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  16. Nahor87 Registered Member

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    Don't panic
     
  17. DaveC426913 Valued Senior Member

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    Hm? Oh, I thought we were just posting random bits of stuff we like.
     

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