Bond Enthalpy Equation Balancing

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Alex Nguyen 3I
Posts: 100
Joined: Fri Sep 25, 2015 3:00 am

Bond Enthalpy Equation Balancing

Postby Alex Nguyen 3I » Thu Jan 28, 2016 8:34 pm

Use the bond enthalpies given in the table below to estimate the reaction enthalpy for burning 1 mol of Butane:
C4H10 (g) + O2 (g) --> CO2 (g) + H20 (g)
The answer was -2186kJ and I got -4372kJ from balancing the equation using whole numbers, which is double the answer. How would you know to use 13/2 moles of O2 instead of 13?

Tara 2K
Posts: 13
Joined: Fri Sep 25, 2015 3:00 am

Re: Bond Enthalpy Equation Balancing

Postby Tara 2K » Thu Jan 28, 2016 9:46 pm

If you balance the equation using whole numbers, the coefficient for butane would be 2 and so that would be the reaction enthalpy for burning 2 mol of butane, but the question asks for the reaction enthalpy for burning 1 mole of butane. Therefore, you would use the coefficients that correspond with 1 mole of butane (13/2 mol oxygen, 4 mol CO2, 5 mol H2O).


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