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Favored products (really a conceptual) question

  1. May 7, 2013 #1
    Bear with me, please. My knowledge of Gibbs, bond formation, entropy and enthalpy is weak, and I think they're needed to figure this out.

    Suppose I have "some" sulfuric acid and "some" salt, and I mix them. At least two reactions are possible:

    H2SO4 + NaCl -> Na2SO4 + HCl
    H2SO4 + NaCl -> NaHSO4 + HCl​

    (I have intentionally left out coefficients) the stochiochemistry of the inputs does not (necessarily) determine the outcome: an excess of one reagent might pass unreacted through to the end of the equation, leaving either one a legitimate outcome.

    So we have several forces warring with one another:
    1) The stochiochemistry of the reactants
    2) Entropy
    3) The "energy level" of the sulfate vs bisulfate
    4) The input energy (heat)​

    So two questions:
    1) How do I know what product will be favored under what conditions? vs
    2) How do I arrange conditions such that a particular product will be favored?​

    Thanks kindly for any insight.
    -Jeff
     
    Last edited: May 7, 2013
  2. jcsd
  3. May 7, 2013 #2
    remember that sodium hydroxide is NaOH and sodium chloride is NaCl
     
  4. May 7, 2013 #3
    Fixed.
     
  5. May 7, 2013 #4
    *) looks like sulphuric acid reacts with solid sodium chloride in low temperature to produce hydrogen chloride and sodium hydrogensulphate

    *)The reaction can also yield [tex]Na_2SO_4[/tex] with concentrated sulfuric acid (and/or eventually [tex]Cl_2(g))[/tex]

    *)
    [tex]Na_2SO_4(aq) + H_2SO_4(aq) <=> 2NaHSO_4(aq) [/tex]
    In fact, the equilibrium is complex, depending on concentration and temperature...
     
  6. May 7, 2013 #5
    Sodium hydrogensulfate is another name for sodium bisulfate, as in equation 2 in the initial post. So, yes! It is one of the possible products.

    Precisely. Which is why I asked:

    Is there something I can do to make my questions more clear, or frame them more carefully?

    -Jeff
     
  7. May 8, 2013 #6

    Borek

    User Avatar

    Staff: Mentor

    Technically all chemistry one learns throughout whole course (doesn't matter whether it is a HS level, or graduate) is about understanding all details to be able to predict reaction outcome - so the answer to your question is not something for a random forum thread :wink:

    To make sulfuric acid react with sodium chloride you generally need solid NaCl and concentrated acid, otherwise you will end with a solution containing all possible ions. All involved substances are well soluble, both acids are strong and 100% dissociated (HSO4- is weaker, but it doesn't change the outcome by much). So the only way of getting the reaction going is to not use water to avoid dissolution and dissociation. That will also allow gaseous HCl to run away, shifting the equilibrium to the right (you may think about it as an entropic element).
     
  8. May 8, 2013 #7
    Admin Borek, thank you kindly for this reply. Sometimes the only (real) answer is "That's a hard problem".

    -Jeff Evarts
     
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