Final answer:
The combustion of methane releases 890.4 kJ of heat energy in an exothermic reaction and can be explored using stoichiometry and Hess's Law to understand the enthalpy changes of chemical reactions.
Step-by-step explanation:
The combustion of methane is a chemical reaction that can be analyzed using stoichiometric calculations as well as Hess's Law to understand the enthalpy changes involved. When 1 mole of methane is combusted, it results in an exothermic reaction, releasing 890.4 kJ of heat energy. This can be represented by the thermochemical equation:
CH4(g) + 2O2(g) → CO2(g) + 2H2O(l) + 890.4 kJ
The concept of Hess's Law demonstrates that the enthalpy change of a chemical reaction is the same regardless of the steps taken to perform that reaction. For instance, the formation of CO2(g) from its elements can be thought of as occurring in two steps that sum to the overall reaction as according to Hess's Law:
2C(s) + O2(g) → 2CO(g) ΔH = -221.0 kJ
C(s) + O2(g) → CO2(g) ΔH = -393.5 kJ
These steps can be added or manipulated in order to find the enthalpy changes for reactions that are not directly measured but are instead derived from known values.