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Titration with Carbonates acting as bases

  1. May 29, 2007 #1
    1. The problem statement, all variables and given/known data

    when a carbonate acts as a base and neutralises an acid, CO2 is formed. the problem is that some of the CO2 dissolves in the water and forms Carbonic Acid.the Carbonic acid will affect the titre value as it will react with the base, along with the HCl. How do we prevent this to happen?


    2. Relevant equations

    Na2CO3 + HCl -----> 2NaCl + CO2 + H2O

    CO2 + H2O ------> H2CO3


    3. The attempt at a solution

    what i'm thinking of is that, by heating the flask containing the titrating mixture as the titration is performed, the CO2 may dissolve out of the water.....

    Is it a good solution? If you have any other suggestion, let me know,
     
  2. jcsd
  3. May 29, 2007 #2
    Is there any way that you could think of that could throw off the equlibrium?
     
  4. May 31, 2007 #3
    Yeah, you're right; i can eliminate the CO2 by just added a lil' bit more of the Na2CO3....

    thnx....

    but the heat thing also works perfect, since solubility of a gas decreases with increase in temperature.
     
  5. May 31, 2007 #4

    chemisttree

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    This won't work. You are titrating an unknown amount of carbonate with an acid. Adding additional carbonate will skew your results.

    The heating idea is good. Sparging or vacuum degassing also works.
     
  6. May 31, 2007 #5
    Heating is probably your best bet. It will be the simplest for you unelss you are just doing the problem for homework. Then you could just mention the various ways.
     
  7. Jun 10, 2007 #6
    hey chemisttree can you explain to me in more detail why the saturation of the solution with the carbonate won't work....
     
  8. Jun 11, 2007 #7

    chemisttree

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    Well, you ARE trying to titrate an unknown amount of carbonate. How will adding additional carbonate help you with that?
     
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