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Homework Help: Energy required for a chemical reaction

  1. Sep 26, 2012 #1
    Hi all,

    I'm looking for the energy required for a 2-step chemical reaction:

    CaSO4 + S2 -> CaS + 2SO2
    CaS + 3CaSO4 -> 4CaO + 4SO2

    This reaction is to happen around 1600 deg. F. I solved for the heat of reaction for these two reactions with the following enthalpy equation: H2=H1+∫CpdT I used the heat capacity correlations from the Perry's Chemical Engineers' Handbook.

    I found the overall energy required for these two reactions in terms of H2, but I'm afraid it may be wrong. My final answer for a temperature of 1600 deg. F is 2,818 kJ/mol.

    I'm wondering if I went about this calculation correctly. I did not solve for the activation energy with the Arrhenius equation, is that something I should have done instead?

    Any insight will be greatly appreciated.
  2. jcsd
  3. Sep 27, 2012 #2
    Firstly when you say "energy required" are you meaning an activation energy to get the reaction started, or to calculate an energy (endotherm) per mole of product needed to drive the reaction?

    If it is the latter that you are after, then the most important thing is to remember that enthalpy is a state function, and therefore independent of path. That means that the activation energy becomes quite irrelevant, and that you can make a calculation by first considering the (quite impractical) reaction at 25°C using tabulated data, and then adjusting by cooling your reactants from actual reaction temperature to 25°C and warming your products from 25°C to the actual reaction temperature using the heat capacity equations.
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