For the oxidation of glucose, ΔHº = -2808 kJ/mol. If 25% of this energy is used for muscle work, how many grams of glucose are required for a 100 kg man to climb a 500-meter hill? (g = 10 m/s²)
Correct answer: D. 120 gm
- A. 100 gm
- B. 180 gm
- C. 200 gm
- D. 120 gm
Explanation
First, calculate the work done: W = mgh = 100 kg × 10 m/s² × 500 m = 500,000 J. The total chemical energy needed is 500,000 J / 0.25 = 2,000,000 J, or 2000 kJ. The mass of glucose required is (2000 kJ / 2808 kJ/mol) × 180 g/mol ≈ 128 g.
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Thermochemistry measures energy changes in chemical reactions and distinguishes exothermic from endothermic processes. Work covers systems, surroundings and state functions, internal energy, the first law of thermodynamics, enthalpy and Hess's law, including the sign conventions used when heat enters or leaves a system.
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