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

Homework Help: Thermochemistry: Heat of a Solution

  1. Jun 29, 2010 #1
    1. The problem statement, all variables and given/known data

    The heat of solution of potassium acetate (KC2H3O2) in water is -15.3 kJ/mol.
    If 12.7 g of KC2H3O2(s) is dissolved in 525 mL of water that is initially at 22.2 °C, what will be the final temperature (in degrees Celcius) of the resulting aqueous solution?

    2. Relevant equations

    Unsure. I used:

    deltaE = C * deltaT

    3. The attempt at a solution

    First calculating moles: 12.7g / 98.1417g/mol = 0.1294047281 mol

    Secondly, calculating kJ per mole: 0.1294047281 mol * -15.3kJ/mol = -1.97989234kJ -> -1979.89234 J

    Third, sub into equation: -1979.89234J / (4.18 J/g * 537.7g) = deltaT

    deltaT = -0.880897256
    22.2 degrees - 0.880897256 = 21.31910274

    The answer is incorrect. I use an online homework system and the following answers are incorrect:

    21.3
    21.2
     
  2. jcsd
  3. Jun 30, 2010 #2

    Borek

    User Avatar

    Staff: Mentor

    If heat of solution is negative, does it mean heat is produced, or absorbed? And should the final temp be higher or lower than initial?

    --
    methods
     
  4. Jun 30, 2010 #3
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook