Question

Find the change in entropy (in cal/k) of $1$ mole of $O_2$ gas ($C_v=5/2R$), when it is
(a) heated from $300K$ to $400K$ isobarically
(b) heated from $300K$ to $400K$ isochorically (Given: $\ln 3=1.1,\ln 2=0.7$)

Answer 1

In Isochoric process, $\Delta S=n{C}_V\ln \left(\frac{T_2}{T_1}\right)$

$⟹\Delta S=1\times \frac{5}{2}R\times \ln \left(\frac{4}{3}\right)$

$⟹\Delta S=1.5$ $cal{T}^{-1}$

In Isobaric process, $\Delta S=n{C}_P\ln \left(\frac{T_2}{T_1}\right)$

$⟹\Delta S=\frac{7}{2}R\times \ln \left(\frac{4}{3}\right)$

$⟹\Delta S=2.1$ $cal{T}^{-1}$