mmart22 stalio 11/20/17 3 This is a Mixed question/It is worth 1 point /You have

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mmart22 stalio 11/20/17 3 This is a Mixed question/It is worth 1 point /You have unlimited attempts / 11 Question (1 point) See page 39Z The enthalpy change for a chemical reaction is the sum of the energy consumed in breaking bonds and the enersy released during bond formation One way to determine the overall energy change for a chemical reaction is to apply Hess's law to add together a group of reactions which can be arranged such that the chemical equations, when combined, give the overall equation we are trying to characterize. 1st attempt did see Periodic Table SeeHint Part 1 (0.3 point) Feedback Write a balanced chemical equation for the combustlion of gaseous propane in gaseous oxygen to produce gaseous carbon diox liquid water See Hint Part 2 (0.3 point) Feedback VIEW SOLUTION

Explanation / Answer

1) Balanced equation,

C3H8 + 5O2 --> 3CO2 + 4H2O

2) invert the first equation,

Multiply the second IInd equation with 3,

multiply the IIIrd equation with 4,

Add all three equations,

C3H8 ---> 3C + 4H2

3C + 3O2 ---> 3CO2

4H2 + 2O2 ---> 4H2O

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C3H8 + 5O2 ---> 3CO2 + 4H2O

dHrxn = +103.8 + 3 x -393.5 + 4 x -285.8 = -2219.9 kJ

3) moles of propane = 20 kg/44.1 g/mol = 0.4535 kmol

Energy relesed by burning this much propane = 0.4535 x 10^3 mol x -2219.9 = 1.01 x 10^6 kJ

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