The following questions concern the combustion reaction of ethane at 298 K: 2 C_

Question

The following questions concern the combustion reaction of ethane at 298 K: 2 C_2H_6(g) + 7 O_2(g) rightarrow 4 CO_2(g) + 6 H_2O(l) delta H degree_rxn = 3119.7 kl/mol a. Is this reaction endothermic or exothermic? b. Based on the above reaction, how much heat is released with the production of 4.55 kg of carbon dioxide at 298 K at constant pressure? c. Use the provided table to calculate delta H_rxn for the above reaction at 398 K. d. The standard enthalpy of vaporization of water at 298 K is 43.99 kJ/mol. Based on this, determine delta H degree_rxn for the combustion of ethane when gaseous is produced (instead of liquid water) at 298 K.

Explanation / Answer

a. dH for the reaction is -ve, so the reaction is exothermic in nature

b. moles CO2 = 4.55/44 = 0.103 kmol

4 mol CO2 produced = -3119.7 kJ of heat,

so, 0.103 kmol CO2 would produce = 0.103 x 10^3 x -3119.7

                                                          = -321.33 kJ of heat

c. dHrxn = [(4 x 37.11 + 6 x 75.29) - (2 x 52.63 + 7 x 29.36)(398 - 298)]/1000 - 3119.7

              = -3090.76 kJ at 398 K

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