Enthalpy of combustion of CH4,C2H6 and C3H8 are -210.8, -368.4 and -526.2 k cal mol−1 respectively. Enthalpy of combustion of hexane can be predicted as ?
-1000 k cal mol−1
ΔHC(C2H6)−ΔHC(CH4)=−368.2−(−210.8)=−157.4ΔHC(C3H8)−ΔHC(C2H6)=−526.2−(−368.4)=−157.8Thus,average ΔHC(−CH2)=157.4+157.82=−157.6 k cal mol−1Then,ΔHC(C6H14)=ΔHC(C3H8)+3ΔHC(−CH2)=−526+3(−157.6)=−999 k cal