Question

Calculate the calorific value of octane. Octane is a component of gasoline with the help of the following reaction.

2C₈H₁₈(l) + 25O₂ ---- 16CO₂ + 18H₂0 delta H= -10920kJ

Answer 1

Here, two moles of octane gives = -10920 KJ heat
So, 1 mole of octane will release = -10920/2 = -5460 KJ of heat.
Now, molar mass of octane = 12 x8 + 1 x 18 = 114 gm = 0.114 Kg
So, 0.114 Kg of octane r = eleases = -5460 KJ heat.
So 1 kg of octane will release =-5460 x 0.114 = -622.4 KJ
Since, calorific value is the energy stored in per kg of the molecule.
Hence, calorific value of octane = - 622.4 KJ/Kg