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Homework Help: Delta H for 25.0 g NaOH in 100ml of 31.5% HCl

  1. Jan 23, 2010 #1
    1. The problem statement, all variables and given/known data
    How do I calculate delta H given the above info and knowing the specific heat capacity of
    H2O and that the change in temperature when the 2 react is 6.2 degrees C

    2. Relevant equations

    3. The attempt at a solution

    Using Q = mcdeltatheta where
    m=mass and
    c=specific heat capacity of H2O (Using H2O's specific heat capacity because there is an aqueous environment here)
    delta T - 6.2 degrees C
    Finding Q then substituting in for deltaH = m x delta T x Q
    Is this the right way to go about finding delta H for this problem?
  2. jcsd
  3. Jan 24, 2010 #2


    User Avatar

    Staff: Mentor

    Yes and no. Yes - that's the corect approach. No - assumption that you should use specific heat of water is in general wrong, as it works reasonably well for diluted solutions, 31.5% HCl is not diluted (10M), adding 25.0 g of NaOH won't dilute it much. But if you have no access to tables of specific heat as a function of solution concentration, this assumption is better than nothing.

  4. Jan 24, 2010 #3
    Thank you
  5. Jan 24, 2010 #4
    Re: delta H for 100ml of 1.0 mol/L HCl with 100ml. of 1.0 mol/L NaOH

    In this case, mixing 2 aqueous solutions, how would I calculate delta H without a value for mass?
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