Which of the following gas will liberate maximum heat on combustion, per gram? — Thermodynamics and Thermochemistry Chemistry Question

💡 Solution & Explanation

The fuel value (or calorific value) of a gas is the heat liberated per gram of the fuel. Methane ($CH_4$) has the highest hydrogen-to-carbon ratio among all hydrocarbons, giving it the highest heat of combustion per gram (≈ 55.6 kJ/g or 13.3 kcal/g). Ethane, ethylene, and acetylene have lower hydrogen percentages by mass, resulting in lower fuel values per gram.