Calculate the enthalpy of combustion of methyl linoleate

Question

Calculate the enthalpy of combustion (in kJ) of methyl linoleate (C₁₉H₃₄O₂), an important component of many biodiesel fuels made from corn oil and methanol, given the following standard enthalpies of formation: CO₂(g) = -393.5 kJ/mol H₂O(l) = -285.8 kJ/mol C₁₉H₃₄O₂(l) = -645.7 kJ/mol

Answer 1

Write the balanced equation for the combustion of C₁₉H₃₄O₂:

2 C₁₉H₃₄O₂(l) + 53 O₂(g) ==> 38 CO₂(g) + 34 H₂O(l) ... balanced equation

∆Hcombustion

∆H = ∑∆Hf products - ∑∆Hf reactants

∆H = [(38 x -393.5) + (34 x -285.8)] - (2 x -645.7) = (-14,953 + -9717) - (-1291)

∆H = -24,670 + 1291

∆H = 25,961 kJ

(be sure to check the math)