To determine the energy released when 81.86 grams of hexane is burned, we need to convert the mass to moles, calculate the moles of CO2 produced, and use the enthalpy of reaction to calculate the energy released. The energy released is -23,710,200 J.
To determine the energy released when 81.86 grams of hexane is burned, we need to first convert the mass of hexane to moles. The molar mass of hexane is 86.20 g/mol, so we divide the mass by the molar mass to get the number of moles:
Number of moles = 81.86 g / 86.20 g/mol = 0.949 mol
Next, we use the balanced equation of the combustion of hexane to determine the moles of CO2 produced. From the equation, we can see that 2 moles of hexane produce 12 moles of CO2. So, for 0.949 mol of hexane:
Moles of CO2 = 0.949 mol * 12 mol CO2 / 2 mol hexane = 5.694 mol CO2
Now, we can calculate the energy released using the enthalpy of reaction. The enthalpy of reaction is given as -4163.0 kJ/mol. So, for 5.694 mol of CO2:
Energy released = -4163.0 kJ/mol * 5.694 mol CO2 = -23,710.2 kJ
To convert kJ to J, we multiply by 1000:
Energy released = -23,710.2 kJ * 1000 = -23,710,200 J
Therefore, 81.86 grams of hexane will release -23,710,200 J of energy when burned.