The plot in Figure illustrates the reaction enthalpy for the combustion of alkanes (C₁ to C₁₀) as a function of the number of carbon atoms (n) using multiple Density Functional Theory (DFT) computational methods, including B2PLYP, B3LYP, LSDA, PBE, TPSS, and dispersion-corrected DFT, all with the 6-31G(d) basis set. Experimental values, represented by the dashed line, provide a benchmark for comparison . Across all methods, the reaction enthalpy exhibits a linear decrease with increasing carbon number, consistent with the exothermic nature of alkane combustion, where longer hydrocarbon chains release greater energy due to the higher number of C-H and C-C bonds oxidized during the reaction. When compared to experimental results, deviations are observed for all computational methods. For smaller alkanes (n=1 to n=3), LSDA and dispersion-corrected DFT show closer agreement with experimental values, whereas for larger alkanes (n≥5), noticeable discrepancies arise. Hybrid methods such as B3LYP and B2PLYP tend to predict slightly lower enthalpy values relative to LSDA and TPSS. Additionally, the annotation for n=6 highlights non-convergence issues for Rung 2 and Rung 3 functionals, PBEPBE and TPSSh, indicating computational limitations or numerical instabilities for intermediate chain lengths. These results emphasize the method-dependent accuracy of DFT in predicting reaction enthalpies, particularly for extended hydrocarbon systems. While higher-rung functionals, such as B2PLYP and TPSS, incorporate advanced exchange-correlation approximations, deviations persist, especially for larger alkanes where dispersion interactions and electron correlation effects are more pronounced. This comparison underscores the importance of refining DFT methods and incorporating appropriate corrections to achieve better agreement with experimental thermodynamic data for combustion systems. Figure is representing the enthalpy calculated by different DFT functionals but with correlation-consistent cc-pVDZ basis set. This plot is showing similar trend to that of split-valence basis set. This basis set could calculate change in enthalpy for all the alkanes with functionals from each Rung of Jacob's ladder. The plot in Figure presents the Gibbs free energy change for the combustion of alkanes (C₁ to C₁₀) as a function of the number of carbon atoms (n) using various DFT methods. The results show a clear linear decrease in Gibbs free energy with increasing carbon number, reflecting the increasingly exergonic nature of alkane combustion as the molecular size grows. While all methods follow a similar linear trend, slight deviations between methods are observed, particularly for larger alkanes. Methods like LSDA and dispersion-corrected DFT predict lower Gibbs free energy changes compared to hybrid methods like B3LYP and B2PLYP, which display slightly higher values. The consistent linear relationship aligns with thermodynamic expectations, where Gibbs free energy becomes increasingly negative as the combustion of longer hydrocarbons releases more energy under standard conditions. These results further emphasize the sensitivity of Gibbs free energy predictions to the choice of functional and the importance of considering dispersion effects for improved accuracy in modeling combustion thermodynamics. Figure which is based on cc-pVDZ basis set shows similar trend to that of split-valence basis set. Entropy change (ΔS) represents the change in disorder or randomness during a reaction and plays a crucial role in determining reaction behavior. A negative entropy change means that the system becomes more ordered during the reaction, with a decrease in overall randomness. This suggests that the products of the reaction are less disordered than the reactants, reflecting a shift toward a more stable and structured state.