Question

If work done by a gas is $142.8\, J$ when heat given to the gas in isobaric process is $500\, J$, then the gas is

• A. $O _{2}$
• B. $NH _{3}$
• C. $He$
• D. $SO _{2}$

Answer 1

Answer: (A)

$W=P\left(V_{2}-V_{1}\right)=n R T_{2}-n R T_{1}$
$T_{2}-T_{1}=\frac{W}{n R}$
$Q=n C_{p}\left(T_{2}-T_{1}\right)$
$500=n C_{p} \frac{W}{n R}$
$500=\frac{C_{p} W}{R}$
$C_{p}=\frac{500 R}{142.5}=3.5 R=7 / 2 R$
Hence, gas is diatomic $O _{2}$