The complete combustion of methane is represented by the thermochemical equation
CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(l) ΔH° = –8.90 × 102 kJ (per reaction as written, at 298 K)
A laboratory burner consumes 25.0 g of CH4(g) while heating a water bath.
(a) Calculate the number of moles of CH4 that are consumed.
(b) Determine the enthalpy change, in kilojoules, associated with the complete combustion of this mass of methane. Report the value with the correct sign and appropriate significant figures.
(c) Explain, in terms of energy flow between the system and surroundings, why the sign of ΔH° for the combustion reaction is the same as the sign you reported in part (b).