Question

Which law of the thermodynamics helps in calculating the absolute entropies of various substances at different temperatures?

• A. First law
• B. Second law
• C. Third law
• D. Zeroth law

Answer 1

The correct option is C Third law

The third law of thermodynamics helps to calculate the absolute entropies of pure substances at different temperatures.
The entropy of the substance at temperature $T$ may be calculated by the measurement of heat capacity change

$\Delta S=S_T-S_0={\int }_0^T\frac{C_{P}dT}{T}$

$\Delta S=C_p.\ln T=2.303C_p.\log T$

Note:
$S_T=$ Entropy at $T$ $K$

$S_0=$Entropy at $0K$