Q. This 16-part problem illustrates the use of experimental data from bomb calorimetry and other sources, combined with thermodynamic relations derived in this and earlier chapters, to evaluate the standard molar combustion enthalpy of a liquid hydrocarbon. The substance under investigation is n-hexane, and the combustion reaction in the bomb vessel is
C6H14 (l) + 19/2O2(g) → 6CO2(g) + 7H2O(l)
Assume that the sample is placed in a glass ampoule that shatters at ignition.
States 1 and 2 referred to in this problem are the initial and final states of the isothermal bomb process. The temperature is the reference temperature of 298.15K.
(a) Begin by using the masses of C6H14 and H2O placed in the bomb vessel, and their molar masses, to calculate the amounts (moles) of C6H14 and H2O present initially in the bomb vessel. Then use the stoichiometry of the combustion reaction to find the amount of O2 consumed and the amounts of H2O and CO2 present in state 2. (There is not enough information at this stage to allow you to find the amount of O2 present, just the change.) Also find the final mass of H2O. Assume that oxygen is present in excess and the combustion reaction goes to completion.
(b) From the molar masses and the densities of liquid C6H14 and H2O, calculate their molar volumes.
(c) From the amounts present initially in the bomb vessel and the internal volume, find the volumes of liquid C6H14, liquid H2O, and gas in state 1 and the volumes of liquid H2O and gas in state 2. For this calculation, you can neglect the small change in the volume of liquid H2O due to its vaporization.