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Homework Help: Thermochemistry Help

  1. Jul 4, 2010 #1
    1. The problem statement, all variables and given/known data

    When 2.0 g of NaOH were dissolved in 53.0 g water in a calorimeter at 24.0 degrees C, the temperature of the solution went up to 33.7 degrees C.

    2. Relevant equations

    Enthalpy change is equal to the opposite sign of the heat of water.

    3. The attempt at a solution

    For enthalpy change of the reaction, I got -2.1 x 103 joules.

    To find enthalpy change for the solution of 1 g NaOH in water, it would just be -2.1 x 103 divided by 1 g, right?

    And to find enthalpy change for the solution of one mole NaOH, it'd be -1.2 x 103 divided by 1 mole, right?

    Now, the equation of the NaOH dissolving in the water would be like this.

    NaOH ---> Na + OH

    Is this right?

    It then asks me to look at enthalpies of formation as given in thermodynamic tables. I am to calculate enthalpy change for the reaction as written in the equation and I should compare it with the enthalpy change for one mole NaOH.

    I'm looking at the table and NaOH is -425.6 kJ/mol. The Na is -240.1 kJ/mol and the OH is -230.0 kJ/mol.

    What now? Isn't the NaOH supposed to match up with what I got previously for one mole?
  2. jcsd
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