Question

The combustion of methane is represented by the following chemical equation:

CH4(g) + 2O2(g) Right arrow. CO2(g) + 2H2O(g) + energy

Is this reaction endothermic or exothermic?

Answer 1

The reaction is exothermic — it releases energy. Energy appears on the product side, and the enthalpy change for combustion of methane is negative (ΔH°comb ≈ −890 kJ mol−1), meaning heat is given off as CH4 and O2 form CO2 and H2O.