Question

The propane fuel (c3h8) used in gas barbeques burns according to the following thermochemical equation: c3h8(g) 5o2(g)→3co2(g) 4h2o(g),δh∘rxn=−2217kj if a pork roast must absorb 1.7×103 kj to fully cook, and if only 14 % of the heat produced by the barbeque is actually absorbed by the roast, what mass of co2 is emitted into the atmosphere during the grilling of the pork roast?

a. 8.72kg
b. 12.14kg
c. 17.59kg
d. 24.07kg

Answer 1

To calculate the mass of CO2 emitted during the grilling of a pork roast, the total heat produced by the barbecue is found first, based on the heat needed to cook the roast and the percentage absorbed. The total heat is used to calculate the moles of propane and CO2 produced, which is then converted to mass of CO2. However, the calculated mass does not match any of the given options.

Step-by-step explanation:

The question involves calculating the mass of CO2 emitted from burning propane (C3H8) when cooking a pork roast. Given that the pork roast must absorb 1.7×103 kJ to cook and only 14% of the heat from the barbecue is absorbed by the roast, we need to calculate the total heat produced by the burning of propane.

The total heat needed is 1.7×103 kJ ÷ 0.14 = 1.214×104 kJ. The reaction enthalpy for propane is −2217 kJ/mol. Using the stoichiometry of the reaction, 1 mol of propane produces 3 mol of CO2. By calculating the moles of propane needed to produce the total heat, and subsequently, the moles of CO2 produced, we can then convert the moles of CO2 to mass.

To produce 1.214×104 kJ: Moles of propane required = 1.214×104 kJ ÷ 2217 kJ/mol = 5.47 mol of propane. Moles of CO2 produced = 5.47 mol × 3 = 16.41 mol. Mass of CO2 = 16.41 mol × 44.01 g/mol = 721.85 g or 0.722 kg of CO2.

Since the amount of CO2 produced is significantly less than any of the provided options in the question, there may be an error in the initial setup or values provided in the question, or in the understanding of the question. Therefore, an accurate answer cannot be provided for the given options.