For a monoatomic gas, work done at constant pressure is $\mathrm{W}$. The heat supplied at constant volume…

For a monoatomic gas, work done at constant pressure is $\mathrm{W}$. The heat supplied at constant volume for the same rise in temperature of the gas is
  1. $\mathrm{W}$
  2. $\frac{5 \mathrm{~W}}{2}$
  3. $\frac{\mathrm{W}}{2}$
  4. $\frac{3 \mathrm{~W}}{2}$

Solution

Heat supplied at constant pressure, $\mathrm{Q}_1=\mathrm{nC}_{\mathrm{p}} \Delta \mathrm{T}$ Heat supplied at constant volume, $\mathrm{Q}_2=\mathrm{nC}_{\mathrm{v}} \Delta \mathrm{T}$ Work done, $\mathrm{W}=\mathrm{Q}_1-\mathrm{Q}_2=\mathrm{n}\left(\mathrm{C}_{\mathrm{p}}-\mathrm{C}_{\mathrm{v}}\right) \mathrm{dT}$ $\begin{aligned} & \frac{\mathrm{W}}{\mathrm{Q}_2}=\frac{\mathrm{C}_{\mathrm{p}}-\mathrm{C}_{\mathrm{v}}}{\mathrm{C}_{\mathrm{v}}}=\frac{\mathrm{C}_{\mathrm{p}}}{\mathrm{C}_{\mathrm{v}}}-1=\frac{5}{3}-1=\frac{2}{3} \\ & \mathrm{Q}_2=\frac{3 \mathrm{~W}}{2} \end{aligned}$

Asked in: MHT CET 2021 (20 Sep Shift 2)

Practice more Thermodynamics questions on Aicharya