Question

A heat reservoir at 900 K is brought into contact with the ambient at 300 kJ of heat is lost by the heat reservoir. The total los in availability due to this process is

• A. None of these
• B. 9000 kJ
• C. 6000 kJ
• D. 18000 kJ

Answer 1

The correct option is C 6000 kJ

(c)
Given data:
$T=900K$
$T_0=300K$
$Q=9000kJ$

change in universe entropy,
$\Delta S_{uni}=-\frac{Q}{T}+\frac{Q}{T_0}$
$=-\frac{9000}{900}=\frac{9000}{300}$
$=-10+30=20kJ/K$
Total loss in availability (= Irreversibility),
$I=T_0\Delta S_{uni}$
$300\times 20=6000kJ$