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Effect on Enthalpy Changes By Using HNO3 Instead of HCl

  1. Aug 21, 2009 #1
    1. The problem statement, all variables and given/known data
    What effect, if any, would using nitric acid instead of hydrochloric acid in the reaction

    NaOH(s) + HCl(aq) --> NaCl(aq) + H2O(l)

    have on the enthalpy changes measured in an experiment?


    2. Relevant equations

    N/A

    3. The attempt at a solution

    I have no idea. Some experimental values I found online suggest that using nitric acid would give a lower enthalpy change value? But I wish to know the reasoning behind this.
     
  2. jcsd
  3. Aug 21, 2009 #2

    Ygggdrasil

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    Science Advisor

    Consider the net ionic equation for both reactions.
     
  4. Aug 22, 2009 #3
    Um after doing that i got the net reaction of
    OH-(aq) + H+(aq) --> H2O(l)
    for both reactions...so does that mean there is no effect???
     
  5. Aug 22, 2009 #4

    Borek

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    Staff: Mentor

    Yes.

    With one important comment. HNO3 is the weakest of the so called strong acids, thus it is not necesarilly 100% dissociated (1% not dissociated in 0.1M solution). Thus enthalpy of the reaction between HNO3 and NaOH has to take HNO3 dissociation into account. No idea how large the difference is and how precise the experiment has to be for the difference to be measurable, but it exists.

    But that's close to nitpicking.

    --
     
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