Air initially at 15°C, 1 bar is heated irreversibly to 303°C, 2 bar. Treat it as calorically perfect, R = 287 J/(kg·K), γ = 1.4. Find entropy change in J/(kg·K), nearest integer.
Entropy is a state function, so use $\Delta s=c_p\ln(T_2/T_1)-R\ln(p_2/p_1)$ despite irreversibility. With $c_p=\gamma R/(\gamma-1)=1004.5$ and temperatures approximately 288 and 576 K, $\Delta s=(1004.5-287)\ln2=497.3$ J/(kg·K). **497 J/(kg·K)**. Using 273.15 gives the same rounded answer.
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