Thermodynamics Question 251
Question: A closed system undergoes a process $ 1\to 2 $ for which the values $ {W _{1-2}} $ and $ {Q _{1-2}} $ are 50 kJ and - 20 kJ respectively. If the system is returned to state 1 and $ {Q _{1\to 2}}+10kJ $ the work done $ {W _{1\to 2}} $ is
Options:
A) 40 kJ
B) 50 kJ
C) -60 kJ
D) -50 kJ
Show Answer
Answer:
Correct Answer: C
Solution:
[c] $ -20=\Delta U+50\Rightarrow \Delta U=-70. $
$ \text{From }2\to 1,\Delta U=70kJ. $
$ \text{Now }10=70+W\Rightarrow W=-60kJ. $
