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In: Chemistry

The enthalpy change for a chemical reaction is the sum of the energy consumed in breaking...

The enthalpy change for a chemical reaction is the sum of the energy consumed in breaking bonds and the energy 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.

The average propane cylinder for a residential grill holds approximately 18 kg of propane. How much energy (in kJ) is released by the combustion of 15.50 kilograms of propane in sufficient oxygen?

Solutions

Expert Solution


balanced equation: C3H8(g)+5O2(g) ---> 3CO2(g)+4H2O(l)

dH°reaction = (3*dH°f(CO2)+4*dH°f(H2O))-(1*dH°f(C3H8)+5*dH°f(O2))

            = (3*-393.5+4*-285.83)-(1*-103.85+5*0)

            = -2220 kj

1 mol Propane = 44 g propane = 2220 kj

no of mol of propane burned = 15.5/44 = 0.3523 kmol

amount of energy released(q) = n*DHrxn

                             = 0.3523*10^3*2220

                              = 7.82*10^5 kj


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