Palmitic acid (Molecular weight $=256.42 \mathrm{~g} / \mathrm{mol}$ ) is one of the major sources o

Question

Palmitic acid (Molecular weight $=256.42 \mathrm{~g} / \mathrm{mol}$ ) is one of the major sources of energy in our diet as shown in the chemical reaction provided below $$ \mathrm{C}_{16} \mathrm{H}_{32} \mathrm{O}_2(\mathrm{~s})+23 \mathrm{O}_2(\mathrm{~g}) \rightarrow 16 \mathrm{CO}_2(\mathrm{~g})+16 \mathrm{H}_2 \mathrm{O}(\mathrm{l}) $$ The energy released by the combustion of 1 g of palmitic acid is. $\_\_\_\_$ kJ/g $\left(\Delta \mathrm{H}_{\mathrm{f}}^{\mathrm{e}}\left(\mathrm{CO}_2\right)=-393.5 \mathrm{~kJ} / \mathrm{mol} ; \Delta \mathrm{H}_{\mathrm{f}}{ }^{\mathrm{e}}\left(\mathrm{H}_2 \mathrm{O}\right)=-285.8 \mathrm{~kJ} / \mathrm{mol} ; \Delta \mathrm{H}_{\mathrm{f}}^{\mathrm{e}}(\mathrm{Cl} 6 \mathrm{H} 32 \mathrm{O} 2)=\right. \left.-891.5 \mathrm{~kJ} / \mathrm{mol} ; \Delta \mathrm{H}_{\mathrm{r}}^0(\mathrm{O} 2)=0 \mathrm{~kJ} / \mathrm{mol}\right)$

Professor PC Thomas Classes · Answer

$\Delta H_{	ext{rxn}} = [16(-393.5) + 16(-285.8)] - [-891.5] \approx -9977$ kJ/mol. Per gram $= -9977 / 256.42 \approx -39$ kJ/g.