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For the reaction: CO (g) + 1/2 O₂ (g) → CO₂ (g);∆H° = - 67650 cal at 25° C. Calculate ∆H° at 100°C, given that the required molar heat capacities are as follows:CP (CO, gas) = 6.97 cal/°CCP (CO₂, gas) = 8.47 cal/°CCP (O₂, gas) = 7.00 cal/°C

Correct answer: A. -67800 cal

  • A. -67800 cal
  • B. -67650.4 cal
  • C. -67762.5 cal
  • D. -54.6 cal

Explanation

Calculate ΔCp (Change in Heat Capacity): Reaction: CO(g) + 1/2 O2(g) → CO2(g). ΔCp = Cp(Products) - ΣCp(Reactants). ΔCp = 8.47 - [6.97 + 0.5(7.00)]. ΔCp = 8.47 - [6.97 + 3.50]. ΔCp = 8.47 - 10.47. ΔCp = -2.00 cal/°C. Calculate ΔT (Change in Temperature): ΔT = 100°C - 25°C = 75°C. Apply Kirchhoff's Equation: ΔH(100°C) = ΔH(25°C) + (ΔCp × ΔT). ΔH(100°C) = -67650 + (-2.00 × 75). ΔH(100°C) = -67650 - 150. ΔH(100°C) = -67800 cal.

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About Thermochemistry and Energetics of Chemical Reactions

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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