Looking for classes? Ksquare Career Institute, Bengaluru →
Choose the correct statement for the work done in the expansion and heat absorbed or released when 5 litres of an ideal gas at 10 atmospheric pressure isothermally expands into vacuum until volume is 15 litres:
A
Both the heat and work done will be greater than zero
B
Heat absorbed will be less than zero and work done will be positive
C
Work done will be zero and heat will also be zero
D
Work done will be greater than zero and heat will remain zero
Detailed Solution
Expansion into a vacuum occurs against zero external pressure ($P_{ext}=0$), so $W=-P_{ext}\Delta V=0$. Since the process is isothermal, $\Delta T=0$, so $\Delta U=nC_v\Delta T=0$. From the first law, $\Delta U=q+W\Rightarrow 0=q+0\Rightarrow q=0$. Both work done and heat are zero.