1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Enthalpy calculation

  1. Jan 24, 2014 #1
    1. The problem statement, all variables and given/known data

    A sample of sulfur, mass 2.56g, is burned in excess oxygen inside a calorimeter of heat capacity 923 J/K and insulated by 815g of water. If the sole product of combustion is SO2(g), what is the expected increase in temperature?


    2. Relevant equations

    q = mcΔT
    q = CΔT


    3. The attempt at a solution

    I am given that the ΔHof = -296.8 kJ/mol for SO2(g) and the enthalpy of formation of oxygen gas and sulfur is 0.

    S(s) + O2(g) → SO2(g)

    So, I did:

    (1g / 32.06 g/mol)(-296.8 kJ/mol) = - [(4.184 g/molK)(815g)ΔT + (923 J/K)(ΔT)]

    After isolating for ΔT and converting units to J, i found my answer as 2.136 K but this is incorrect. Any comments on where I went wrong? Thanks!
     
  2. jcsd
  3. Jan 24, 2014 #2
    A negative heat of reaction means that, to maintain the temperature constant at the initial temperature, you need to remove heat. So the reaction gives off 296.8 kJ/mol. So the temperature in your calorimeter has to rise. There shouldn't be a minus sign on the rhs.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Enthalpy calculation
Loading...