When 5 litres of a gas mixture of methane and propane is perfectly combusted at 0°C and 1 atmosphere, 16 litres of oxygen at the same temperature and pressure is consumed. The amount of heat released from this combustion in kJ (∆Hcomb (CH₄) = 890 kJ mol–1, ∆Hcomb. (C₃H₈) = 2220 kJ mol–1) is (Karnataka NEET 2013)

CH₄ + 2O₂ → CO₂ + 2H₂O C₃H₈ + 5O₂ → 3CO₂ + 4H₂O No. of moles in gaseous mixture THERMODYNAMICS AND THERMOCHEMISTRY 55 CH₄ + C₃H₈ = 5 22.4 = 0.22 moles No. of moles of O₂ = 16 22.4 = 0.71 moles Let x moles of CH₄ is there in a gaseous mixture so, number of moles of C₃H₈ would be 0.22 – x. Then moles of O₂ consumed, 2x + (0.22 – x)₅ = 0.71 or x = 0.13 Total amount of heat liberated = 0.13 × 890 + 0.09 × 2220 = 315.5 kJ