Discussion
The net entropy generation (considering the system and the thermal reservoir together) during the process is closest to :
[given : 1 kJ energy transfer takes place at 400° C, while the increase in the entropy of system is 10 J/K]
Answer: D
The net entropy generation is closest to 8.51 J/K.
The reservoir at 400°C, that is 673 K, gives up 1 kJ, so its entropy falls. The system's entropy rises by 10 J/K.
\[ \begin{aligned} \Delta S_{res} &= -\frac{1000}{673} = -1.49\ \text{J/K} \\ S_{gen} &= 10 - 1.49 = 8.51\ \text{J/K} \end{aligned} \]
The temperature must be in kelvin: using 400 directly would give \(10 - 2.5 = 7.50\) J/K, which is the trap among the options. 10 J/K counts only the system and ignores the reservoir's loss of entropy.
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