Exercise 11 | Lewis Formulas

Chapter 7 - Lewis Formulas

Calculate the change in enthalpy ΔH⁰ of the following reaction:

CH₄ + 2 O₂ → CO₂ + 2 H₂O

Is this an endothermic or exothermic reaction?

Data:

Bond energy (BE):

H-H = 436 kJ.mol^-1

C-H = 413 kJ.mol^-1

C-C = 347 kJ.mol^-1

C=C = 607 kJ.mol^-1

C-O = 358 kJ.mol^-1

C=O = 805 kJ.mol^-1

O-O = 204 kJ.mol^-1

O=O = 498 kJ.mol^-1

O-H = 464 kJ.mol^-1

See Solutions

Solution

ΔH⁰ = 4 BE (C-H) + 2 BE (O=O) – 2 BE (C=O) – 4 BE (O-H) = -818 kJ.mol^-1

ΔH⁰ < 0 ⇒ the reaction is exothermic.