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

How did they come up with this completed reaction

  1. Jun 20, 2012 #1
    This is what the completed reaction looks like
    Na2CO3 + 2HCl ⇔ 2NaCl + H2O + CO2

    My question is how did they get the products in the above reaction.

    Here is my attempt, but I don't see how to get it like in the above reaction
    Na2CO3 + HCl ⇔ NaCl + HCO3

    The HCO3 breaks down as follows:

    HCO3 + H2O ⇔ H3O+ + CO2

    So my question is how did they only get H2O + CO2 in the top reaction without the hydronium H3O+ ??

    Thanks
     
  2. jcsd
  3. Jun 20, 2012 #2
    There is a Na missing.

    Where does the charge comes from?
     
  4. Jun 20, 2012 #3

    Borek

    User Avatar

    Staff: Mentor

    Apart from what DrS wrote, solution of HCl contains plenty of H+.
     
  5. Jun 21, 2012 #4
    Well, the first equation you gave us is balanced. The reactants and products both contain:

    3 O
    2 Na
    2 Cl
    2 H
    1 C

    However, your second equation is missing a coefficient in front of one of the reactants. You wrote: Na2CO3 + HCl ⇔ NaCl + HCO3. This is not balanced properly, because on the reactant side you have 2 Na, and on the product side you only account for 1 Na. If you add a two in front of the HCl in the second equation, you get the correct products for the completed reaction of:

    Na2CO3 + 2HCl ⇔ 2NaCl + H2O + CO2.
     
    Last edited: Jun 21, 2012
  6. Jun 21, 2012 #5
    Heavymetal:

    It's not a question about balancing!!

    I could balance the equation no problem. The question is why the reaction doesn't go this route:

    Na2CO3 + 2HCl ⇔ 2NaCl + H2CO3

    The H2CO3 breaks down as follows:

    H2CO3+ H2O ⇔ H3O+ + HCO3

    The HCO3 breaks down as follows:

    HCO3+ H2O ⇔ H3O+ + CO3

    So I got H3O+ + CO3 but why is it that the correct reaction has H2O + CO2 (at the top, at the beginning of this post) without the hydronium ion H3O+ and CO3 ??
     
  7. Jun 21, 2012 #6
    Are you serious in asking me where the +ive charge on a hydronium ion came from????
     
  8. Jun 21, 2012 #7
    I believe it goes:

    H2CO3 + 2H2O ⇔ HCO3- + "H3O+" + H2O
    HCO3- + "H3O+" + H2O ⇔ CO32- + 2"H3O+"
    CO32- + 2"H3O+" ⇔ 3H2O + CO2

    I say "H3O+" because it doesn't actually take shape of the hydronium ion here. So if you cancel out the 2 H2O from the beginning, and the 2 out of the 3 in the end, you get a net equation that looks like:

    H2CO3 ⇔ H2O + CO2

    However, it probably looks more like this:

    H2CO3 ⇔ HCO3- + H+(aq)
    HCO3- + H+(aq) ⇔ CO32- + 2H+(aq)
    CO32- + 2H+(aq) ⇔ H2O + CO2
     
  9. Jun 21, 2012 #8

    Borek

    User Avatar

    Staff: Mentor

    That's the main equation here, everything else is just an alternative take on the several equilibria present in the solution.
     
  10. Jun 21, 2012 #9
    Yes, I do. The net quantity of electric charge must not change.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: How did they come up with this completed reaction
Loading...