Question

Carbon monoxide is carried around a closed cyclic processes $abc$, in which $bc$ is an isothermal process, as shown in figure. The gas absorbs 7000 J of heat as its temperature is increased from 300 K to 1000 K in going from $a$ to $b$. The quantity of heat ejected by the gas during the process $ca$ is

• A. 4200 J
• B. 500 J
• C. 9000 J
• D. 9800 J

Answer 1

The correct option is D 9800 J

$\Delta Q_{ab}=+7000=\mu C_v(1000-300)$
For the process $ca$:

$T_a=300K,T_c=T_b=1000K$
$\Delta Q_{ca}=\mu C_p(300-1000)=-\mu C_p\times 700$
$=-\mu (C_v+R)700$

For carbon monoxide:
$\gamma =7/5$
$C_v=\frac{R}{\gamma -1}=\frac{R}{\frac{7}{5}-1}=\frac{5R}{2}$
Hence, from equation of $\Delta Q_{ab}$:
$7000=\mu \frac{5R}{2}\times 700$ or $\mu R=20/5=4$
$\Delta Q_{ca}=-\frac{7}{2}\left(4\right)700=-9800J$
Negative sign shows that heat is ejected.