? asked in Science & MathematicsChemistry · 9 years ago

what is the enthalpy of formation of hexane (C6H14) given that the enthalpy of combustion of hexane is?

-4163.2 kJ/mol, the enthalpy of formation of carbon dioxide is -393.5 kJ/mol and the enthalpy of formation of water is -28508?

a) +67.1 kJ/mol

b) +198.4 kJ/mol

c)-198.4 kJ/mol

d) -67.1 kJ/mol

Update:

Its -285.8

4 Answers

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  • 9 years ago
    Favorite Answer

    Combustion reaction is:

    C₆H₁₄ + (19/2) O₂ → 6 CO₂ + 7 H₂O

    The enthalpy of combustion is nothing else than the enthalpy of the combustion reaction:

    According to Hess' law, enthalpy of reaction equals the difference of the enthalpies of formation of products and reactants:

    ∆Hr = (∑ ∆Hf)_products - (∑∆Hf)_reactants = 6∙∆Hf(CO₂) + 7∙∆Hf(H₂O) - ∆Hf(C₆H₁₄) - (19/2)∙∆Hf(O₂)

    Since the enthalpy of formation of the elements at their standard state equals zero:

    ∆Hr = 6∙∆Hf(CO₂) + 7∙∆Hf(H₂O) - ∆Hf(C₆H₁₄)

    Hence,

    ∆Hf(C₆H₁₄) = 6∙∆Hf(CO₂) + 7∙∆Hf(H₂O) - ∆Hr

    = 6∙(-393.5 kJ/mol) + 7∙(285.8 kJ/mol) - (-4163.2 kJ/mol)

    = -198.4 kJ/mol

    answer c) is correct

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  • radel
    Lv 4
    3 years ago

    Enthalpy Of Combustion

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  • 3 years ago

    Enthalpy Of Formation

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  • 5 years ago

    This Site Might Help You.

    RE:

    what is the enthalpy of formation of hexane (C6H14) given that the enthalpy of combustion of hexane is?

    -4163.2 kJ/mol, the enthalpy of formation of carbon dioxide is -393.5 kJ/mol and the enthalpy of formation of water is -28508?

    a) +67.1 kJ/mol

    b) +198.4 kJ/mol

    c)-198.4 kJ/mol

    d) -67.1 kJ/mol

    Source(s): enthalpy formation hexane c6h14 enthalpy combustion hexane is: https://shortly.im/fYgxv
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