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Enthalpy question

  1. Apr 16, 2005 #1
    I'm not really sure what the question is asking for. But my guess is they are asking for which one will output the most energy per mass of the reactants. If this is correct, then im guess the answer is b). If not can some one explain why? Thanks.

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  2. jcsd
  3. Apr 16, 2005 #2


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    the enthalpy is given in terms of moles of reaction, you'll need to read up on this and then relate moles of reaction to moles of the fuel (compound being oxidized) and the oxidant...basically both are reactants.

    energy/{(mass of oxidant)(mass of fuel)}, note it is in terms of mass.
  4. Apr 16, 2005 #3
    What i did was i said the enthalpy represented change in energy/(per reaction). Although it says moles, but that doesn't really make sense since each of the reactants and products have different coefficients.

    So each reaction needs a certain amount of reactants and i simply added up their atomic masses. It seems like hyrogen + 1/2 O2 -> H2O gives the most energy per mass of reactants. But im not sure...
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