Which law of the thermodynamics helps in calculating the absolute...

The third law helps to calculate the absolute entropies of pure substances at different temperature. The entropy of the substance at different temperature. $\mathrm{T}$ may be calculated by the measurement of heat capacity change $$\begin{array}{l}\mathrm{S}_{\mathrm{T}}-\mathrm{S}_{0}=\Delta \mathrm{S}=\int_{0}^{\mathrm{T}} \frac{\mathrm{C}_{\mathrm{p}} \mathrm{dt}}{\mathrm{T}}\\ \text{ Where } \mathrm{S}_{\mathrm{T}}=\text{ Entropy at } \mathrm{T} \mathrm{K} \end{array}$$\mathrm{S}_{0}=$Entropy at$0 \mathrm{ K} $$\begin{array}{l} =\mathrm{C}_{\mathrm{p}} \cdot \log _{e} \mathrm{ T}\\ =2.303 \mathrm{C}_{\mathrm{p}} \mathrm\log \mathrm{T} \end{array}$$$