Thermodynamics Question 239
Question: 4 kg of oxygen gas is heated so as to raise its temperature from 20 to$ 120{}^\circ C $ . If the heating is done at constant pressure, the external work done by the gas is ($ C _{p}=0.219cal/g{}^\circ C $ and )
Options:
A) 628 kJ
B) 104 kJ
C) 366 kJ
D) 206 kJ
Show Answer
Answer:
Correct Answer: B
Solution:
[b] $ W=P(\Delta V)-P( {V _{\gamma }}\Delta T ) $
$ =10^{5}\times {{( 5\times {{10}^{-2}} )}^{3}}\times 3.5\times {{10}^{-5}}\times 375=0.164J $
$ =4( 0.219-0.157 )\times 4200\times ( 120-20 ) $
$ =104\times 10^{3}J $
