Question

Qi. Two litres of an ideal gas at a pressure of 10 atm expands isothermally at 25 °C into a vacuum until its total volume is 10 litres. How much heat is absorbed and how much work is done in the expansion ?

Answer 1

Dear Student
In case of expansion, work is done by the system.
Now, as we know that,
W =−P_ext.​ΔV
As the gas is expanding is vaccum which has no pressure, i.e.,
P_ext.​=0
∴W=0
Hence no work is done.
From first law of thermodynamics,
ΔU=q+W
As the system is working at constant temperature, i.e., isothermally.
∴ΔU=0
Hence, q = -W = 0; q=−W=0
Hence no heat is absorbed in the expansion.

Regards