Task

Complete combustion of 5.6 L (STP) of a methane–ethane mixture (liquid water formed) released 289.515 kJ of heat. Enthalpies of formation (kJ/mol): ΔfH°(CH₄) = −74.8; ΔfH°(C₂H₆) = −84.7; ΔfH°(CO₂) = −393.5; ΔfH°(H₂O, l) = −285.8. 1) Using the corollary of Hess’s law, calculate the enthalpies of combustion of methane and ethane (kJ/mol). 2) Determine the volume fractions (%) of the gases in the mixture. 3) Calculate the volume of air (L, STP) used to burn the mixture (oxygen is 21 % of air by volume). 4) Find the mass of precipitate formed when the combustion products are passed through excess lime water. For every part, show the method (reaction equations, formulas, reasoning) and all calculations step by step.