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    Question is
    a) write a equation for complete combustion of hydrogen
    b) work out enthalpy change using h20 enthalpy of formation as (-285.5)

    This is how I did it:

    a) 2H2+O2=2H2O
    b) -(0)+(-285.5*2)=-285.5*2= -571

    I looked at the mark scheme and got Question a wrong for some reason and obviously if the equation is wrong, so is answer b.
    What I want to know is why the equation has to be h2 + 1/2 O2 = H20 and not what I wrote.
    Please don't write because it is enthalpy of formation because they don't tell you that until the next question
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    For enthalpy of comubstion it is when one mole of a substance combusts
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    (Original post by soup)
    For enthalpy of comubstion it is when one mole of a substance combusts
    Question a has nothing to do with enthalpy.
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    (Original post by nasira372)
    Question a has nothing to do with enthalpy.
    The key point in that user's post was 'one mole' - look at your equation again - can you see where you went wrong?
 
 
 
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