Question

Which of the following reactions represents an exothermic reaction?

A) C + 2S → CS₂, ΔH = 27,550 cal
B) 2H₂O → 2H₂ + O2, ΔH = +58 kcal
C) C (graphite) → C (diamond), ΔH = 0.45 kcal
D) NH₃(g) + 12.0 kcal → ½N₂(g) + 3/2H₂(g)
E) CH₄ + 2O₂ → CO₂ + 2H₂O + 212,800 cal

Answer 1

The reaction CH4 + 2O2 → CO2 + 2H2O + 212,800 cal is exothermic, as it releases heat (212,800 calories) to the surroundings.

Step-by-step explanation:

An exothermic reaction is characterized by the release of heat to the surroundings and a negative value of the enthalpy change (ΔH). In contrast, an endothermic reaction absorbs heat from the surroundings, indicated by a positive ΔH. Considering the choices provided, the reaction that represents an exothermic reaction is:

E) CH4 + 2O2 → CO2 + 2H2O + 212,800 cal

This reaction has a positive heat value listed, meaning 212,800 calories of heat are released when methane (CH4) combusts with oxygen (O2) to form carbon dioxide (CO2) and water (H2O), making it an exothermic reaction.