Asample of a hydrocarbon is combusted completely in o2(g) to produce 21.83 g co2(g), 4.47 g h2o(g), and 311 kj of heat. a) what is the mass of the initial hydrocarbon sample? b) what is the empirical formula of the hydrocarbon? c) calculate the molar enthalpy of formation (hof) of an empirical formula unit of the hydrocarbon. d) identify the hydrocarbon among those listed in appendix c of the textbook. explain your choice.